So, in the comments trail, Keith said:
I have been troubled about a submission I made. I may have made a boneheaded mistake.
I sent a SASE with my manuscript but I cannot remember whether I stamped it or not. It may have been a SAE. if that is the case and you received it, would you reject it and would you not send word about it.
Don't worry about it. I would see the envelope and go "Oops!" and that would be the end of it. If I accepted your manuscript, I probably wouldn't even use the SASE. I'd call or e-mail. If I rejected, and it was a #10 envelope SAE, I'd just stamp it and send the letter in it anyway. If it was a larger envelope, indicating you wanted the entire manuscript back, I'd have my secretary call you and request you send postage or ask permission to toss it. (Unless I'm sending you notes, there's no reason for me to mail the mss back to you because usually it's too hashed for you to send it to another publisher.)
I never accept/reject/read/not read based upon the presence or lack of a SASE. It's only when no SASE is combined with several other things (attitude, weird font or paper, 4 pg query letter, etc.) that I start thinking mean things about the author.
[Will respond to Josi's comment another day.]