I suspect she was looking for something to eat. I spent a little over 1/2 hour with them and she did not return while I was there.
I believe the stump they are playing on is the "roof" of their den.
This was last Thursday afternoon. I returned again on Friday and Saturday but they were nowhere to be found--or heard.
Cubs are amazingly noisy--that is how I was drawn to them. It is not unusual to hear them inside the den.
These have probably been out for a couple of weeks. If I am correct in that it is now time the sow will be ready to begin eating again.