What is the rescue's responsibility?

We adopted an adorable 2 year old terrier last week and he's got medical issues that weren't examined or discussed with us. He's got a UTI, possibly kidney stones, foxtail in his ear, bacterial skin infection, and has a positive initial heartworm test. This rescue pulls dogs from various shelters and sets them up with fosters. The rescue got him neutered, vaccinated, and gave him a dose of flea and heartworm medicine on the day of adoption.

I'm wondering - is this typical? Do rescues or shelters have a responsibility to do more thorough examinations of their dogs prior to adoption? Or we just accept this is a risk with rescue doggos?

He's receiving additional testing and treatment right now of course. I wouldn't give him up but I'm feeling a little like this was a trap.