In this tank I removed a lot of substrate in order to not allow burrowing at the moment.
During last 2 weeks it was waken, but stressed by new environment.
Last 3 days, she spent nights in water bowl, ate a lot, so I was optimistic she was out for a long period.
Yesterday evening, she made a big poop in this bowl, so I changed it and the frog wxent to hide in a new place she never went before...
Result : this morning she was completely burrowed again, at a place where I didn't remove enough substrate...

I put her out of substrate and put her in water bowl.
I will check this evening when I come back to my home if she burrowed again or not.

Except fear or stress, She has no objective reasons to burrow...