Messenger frozen

I have currently a problem with Messenger

it is 'frozen' , means it is not possible to do anything, it does not react to any action on the pushbuttons, it can not be charged, it displays 27% of charge.

I know the way to factory reset via menu, but this can not be reached as the menu buttons are inop. Is there some kind of trick to wake the unit?

It is slightly difficult situation, as I have the device not n my hand, it is on mission far away and with an rather inexperienced user.