[CMB]

If you have another house with an open bottom she may move into that one.

If may be wise to check the food hoard. As the house has a bottom just in case she has peed inside the house. You could wait until she is out running on her wheel or playing etc and remove it to check.

Syrians often choose a corner to pee in. Once a corner is chosen. A litter tray put in that corner and some substrate with pee on put in the tray. The smell attracts the hamster to continue using the tray/pee corner.