My perplexity about someone mailing query without an SASE overlooked the obvious: it was a mistake; the writer intended to include one.
Since I like to make mistakes at least once a day, just to make sure I don't lose my knack for doing so, may I suggest this:
If you're querying by mail, put Enc: SASE under your sig line. That way, if you forget, I know you've forgotten. Same with sample pages. Enc: 5 pages of deathless prose. Same with $20 bills. Ah the stuff that dreams are made of! (Can you tell I just read The Maltese Falcon?)