Is this a one-time occurrence, or do I have to drink from the toilet from now on? If the latter, can I set aside a particular toilet used only for drinking?

From now on and yes you can but guard it well my friend

my co-workers include my wife and my neurotic friend who would never do such a thing, so I guess I won't be drinking from a toilet :P

A urinal implies "public washroom", where-as a toilet could but public or private. For this reason, I'll go with drinking for the toilet.

On the other hand, if both are forced to be "public" then I'd go with washing my face since I'm not ingesting anything.