Yes it is possible he is eating his poop like jersygirl said, bunnies do this sometimes and it is normal, is he eating hay? Vets are open on a Sunday for emergencies, but it will cost a lot of money, it cost £150 for Olly to be sorted out on a Sunday for GI, or if you are in the UK the P.D.S.A will look at bunny and you pay a donation, (If you are on low benefits) they are as good as private vets, keep an eye on him, he might be hiding his poop for a midnight snack, Olly has done that before, but if you do take bunny to a vet on a Sunday be prepared for a big bill, if it is GI it can be expensive, there are antibiotics if the vet says bunny needs them, he is a 5 months old so he’s a baby and may need some help and quickly if he isn’t pooping, give him the best food you can afford for a junior rabbit, Olly is an adult and since I changed his food he doesn’t get GI, he doesn’t hide poop for a snack later as much.