This bike is in perfect shape as a twelve speed, and you live out in the foothills; this is a really dumb question. My response was a bit more diplomatic than my thought process, but essentially I tried my best to talk him into keeping it as a geared bike.
If I was in your shoes; I would gentlely suggest that they ride as it for a little while, find out what gear they are most comfortable riding in, and then bring it back, and you would convert it to a fixie in that gear. It could very well be that they decide having more than one gear is not so bad after all.
I have been somewhat fortunate in having two bikes stolen, and two bikes recovered. The first one was a Varsity; they apparently took it for a joy ride, and ditched it in junked condition.
So, I bought the Viscount to replace it. I was riding it to trade school every day, and chained it up to the same lightpost. One of the guys in the shop convinced his teacher that since he saw the bike there every day, it was abandoned, and his teacher loaned him a pair of chain cutters so he could take it home.
When I reported it stolen, the word got around quickly to the shop teacher, and he drove me personally to the student's house to recover it. It stayed by my drafting table after that.
(Which is why I do not support liberating "abandoned" bicycles unless you know for a fact from the owner that it is abandoned.)
-James