Gizzy's a sprayer, let's face it, and it doesn't take much of a trigger to set him off spraying. You might read my comment in thread "Rocky's spraying again". I think Gizzy's very much like Rocky.
I suspect it was the scent of your friend's cat and 2 dogs likely triggered it. Wash all
the clothes you had on last night, even scrub your shoes, have a shower. Wash everything he peed on. Do you have a large piece of plastic that you can put under
the throw blanket in case he does it again?
In future, just be sure if you visit anyone with cats or dogs, that you strip down, stash the clothes, clean shoes and wash your hands well or have a shower right after coming home. Sorry to hear Gizzy slipped up, but he was doing well for quite while, and hopefully he'll have forgotten about this incident and behave himself.