Thats a bummer.
Sorry that happened. Mistake made, lesson learned, move on. Make a fun project out of it. Life is 20% what happens to you and 80% how you deal with it.
Maybe he knew, maybe he didnt, but it really doesnt matter. Legally, you couldn't prove it either way, and I seriously doubt he gave you a warranty.
It is not his fault you didn't check out the coach before you bought it, and you are obviously capable of doing so. Never trust anyone when it comes to a used vehicle sale.
Might want to be careful with your finance company and insurance finding out though. Not sure, since we havent financed anything in over 15 years, but think they could legally call in your entire balance due, depending on the amount of damage, since their collateral is now gone. With insurance, since there is structural damage, they could consider it a liability on their end and either raise your rates, or cancel your coverage.
Best of luck. Hope your repairs turn out well.