Karl-Peter Gottschalk has a collection of English malapropisms*, except this one, which isn't:
Come to think of it, here is another one that is particularly common in American English. “I felt as if I were….” There is only one of you... [s]o this statement should be “I felt as if I was….”
Except were is also the subjunctive mood of was, which one trots out for just such occasions:
The past subjunctive is sometimes called the were subjunctive, since were is the only subjunctive form that is distinct from the indicative past tense. It appears chiefly in if clauses and in a few other constructions expressing hypothetical conditions....
I'm trying to be less sensitive to the singular their out of necessity, but you can have my subjunctive were when you pry it from my cold, dead lips. (Er, ew.)
* Yes, they aren't word misuses, so my calling them malapropisms is a malapropism.
