Where have my shoes gone?

Wouldn't your warranty claim be contigent on you being able to provide proof of purchase (which would state the date of the transaction) from the retailer, and not on how many times or how many miles you've run in them?

I've just checked both Garmin Connect Mobile apps for Android and for iOS, and my shoes are all listed. I find it very weird that you'd see yours in Garmin Connect online but not in the GCM app, given that the app is just another front-end client accessing the data stored in the cloud. When you review a tracked activity in the GCM app, do you see any gear attached to it, and do you get presented with a list from which to select when you go to Add or Remove Gear?

Re the warranty claim it was only to tell him how many miles is done in them. It wasn't necessary just for info.

I noticed I couldn't add my shoes to the last couple of runs as the options weren't there, but didn't think too much of it. It was only when I tried to figure out why I couldn't that I realised there is no gear listed on the app. I've also realised today that a lot of other info has gone too such as age, weight and height.
All I can think of is that I had to logout the app and close it before logging back in in order to fix a problem when I changed router and nothing was uploading despite changing the password for it. That was over a month ago tho and I'm sure I've added shoes to runs since then.

If the app is just displaying the info on the web version is there any way to make them sync up again?

I dunno. Have you tried removing the Garmin Connect Mobile app, then reinstalling it from the App Store anew? (Yes, that means the rigmarole of giving your Garmin Connect account login credentials again, and pairing your watch again, etc.)

Hmm the mystery deepens!
I went to look at the web version again and my shoes weren't listed under gear, so I went to activities to see if old runs still had shoes tagged to them and suddenly the shoes are back! (Only in the web version) but I also realised there are no runs listed since 27 Dec which is when the router change happened.
They are all in the phone app old and new but with no gear associated with the old ones

Ok I'm getting somewhere...
It's probably worth mentioning that I don't use the web version much cos I find it slow, glitchy and generally annoying!

So it turns out I have 2 different garmin logins! No idea why! both have the same password but one has my email address spelled wrong.

I've obviously logged into the phone app using the wrong one when I had the router problem.

So changing the account I'm using on the phone has given me back my shoes, but I've lost all my runs since 27 Dec.

I have the passwords for both accounts saved on my laptop and I suspect as I click on things in the web version it's using both logins interchangeably! That would answer why sometimes my shoes are there and sometimes not. I even had all my runs up to date at one point!

So now I just need to figure out how to merge all the info from the 2 accounts!
I don't really understand how/why both accounts have all the same runs up to 27 Dec tho!?

If you have the old data on your device still, you can upload directly from there to your account by connecting the device to your computer, logging into the correct account and uploading directly by clicking on the white plus in the blue circle and select Import Data. Either drag and drop or select browse by going to Garmin\Activities on your device

Or to get the old data from Garmin Connect:

Log into Garmin Connect with the incorrect account.
Go into each activity, click the gear icon and select Export Original and save to your computer

Once you have all the ones you want, log out and log into the correct account. Then click on the white plus in the blue circle and select Import Data. Either select Browse and go to where you saved the files and select the files or drag and drop onto the Garmin Connect window.

You will also want to make sure your device is associated with the correct account in Garmin Express. Simplest way is to delete it and re-add with the correct credentials.

Thanks that's really helpful!
Been doing some searching and it seems having 2 accounts is not uncommon but they can't be merged.
That seems the easiest way to transfer data I've read so far...
Not sure how many runs my watch stores (fr620) but it should get a lot of them I'd think, and the rest can be done manually.

I'll try to delete one of the accounts when I'm done - unfortunately the majority of stuff is saved in the one with the misspelled email and when I try to correct it it just logs me into the other one!
If I can't do that I guess I'll just have to remember which one to use and delete the password from my laptop for the other so it can't login automatically.