I have foamed my sill plates also. I used Tiger Foam E84 rated to do mine. I placed a piece of hard core foam in the opening and then sealed it with foam, so I didn't have to use so much per opening.
I did mine 8 years ago with no ill affect. If they used the correct product then there should not be a problem.
If you want to remove it then you must buy the house first then remove it cause I wouldn't want you removing mine(-;
Either way give them a call and see what the experts on the product have to say on removing it or keeping it.