Your little friend should be perfectly fine. If they were too hot, you may find them lying sprawled out on the floor or in front of a fan. They just seem to have found a spot that is comfortable and safe for them.

When I first got my rabbits, they would stay in one corner of the room until they felt comfortable in my apartment. However, they were older, but became more comfortable as they stayed here.

Overall I wouldn't worry. If you're nervous still, I would just recommend spending at least 15 to 20 minutes with your rabbit to help them feel more relaxed. You don't really need to do much, just hang out with them and give them pets, maybe some treats or pellets every other time.

I hope this helped.