It had never happened earlier and I think it has nothing to with the type of Garmi device which was impacted, but all my watchfaces, ciq datafields and ciq widgets have disappeared both from my watch and from the gcm ios app, too.
Since I saw nobody else to complain about it today I think it was triggered by the restart of my watch and my phone at the very same time. Maybe I am wrong, but I have used 4 cow capable Garmin watches and one Edge, and this sort of erase never happened. It happened that some sports app became corrupted or an auto full (hard) reset happened.
I just wished to share it. If my assumption is not totally wrong then one has to take care about how exactly he or she switches off his or her Garmin device and the phone paired to it