How incredibly frustrating!!! I hope your friends apologized!
I've used Resolve before and it doesn't seem as powerful as a couple other ones I like for when our cat decides to
I like Clorox stain remover spray. You can get it in the laundry aisle of the grocery store. It comes in a dark blue spray bottle. It's color safe and works well on carpets (my parents' dog was very sick his last couple years of life and my mom swore by this stuff!). Just spray it on, let it sit for a few minutes and then blot well with a clean dry cloth. Once it's dry you can vacuum to bring the pile of the carpet back.
You can also try a spray cleaner called Awesome. Around here you can find it at the dollar stores. It seems to work on about anything. Just be prepared--it has a strong chemical smell when you spray it. I can't use it because of my asthma, but DH likes it! It doesn't smell once it dries. You use it just like the Clorox spray.