So I had something similar happen with a California king snake. We finally found him behind the wall in our bathroom when we started a remodel. He had become totally wild and had been hunting ALOT of rodents and maybe other snakes or lizards in the wall- hence the renovation. Your snake may have hunted some kind of vermin that was sick or infected with a bacterial or fungal issue thus sickening your snake. This IS NOT likely but should be considered.
The entire series of events was very stressful on him I'm sure, and putting him back in containment after 10 weeks of freedom is part of that. It is normal for snakes not to eat when in a new or changed environment or from any type of stressor. Try NOT to handle him much, if at all until eating becomes regulated again.
If you were feeding frozen before, know that while out he most likely hunted and now has a taste for warm blooded food and his very strong instinct has kicked in, frozen may possibly Never work again. Try live, and also try one size smaller than the typical recommended meal for his size. A small meal is less likely to be regurgitated when he does eat.
Good Luck! And try not to freak out too much captive snakes can go 2-3 months without eating, and adult snakes with slower digestion than juveniles have gone up to 22 months in the wild, although I don't recommend any purposeful purging. Keep trying!
