Yorkshire Terrier Peeing everywhere when staying with friends?

I have a 10 month old Yorkshire Terrier who is house broken when I'm around but seems to forget everything when I have to let him stay with friends. He drips everywhere he goes and will urinate where ever he pleases when he sleeps away. Thankfully he doesn't poop but he just ruined my friends suede couch. Any suggestions on the cause or how to fix it?