Is Hotmail Blocking Gmail Invitations?

This could just be an isolated incident, but last night I got my first Gmail invites, so I sent one to my friend’s Hotmail account and it bounced. So not only may Hotmail be blocking the Gmail invitations (which, honestly, I doubt, but it’s just shady enough to question it), but I wasted an invitation that I won’t get back. Anyone else had this problem?

Update: Thanks to everyone telling me to check the Sent folder. I can at least retrieve the invites now.

Update update: This is interesting comment, too, from reader Alex Nobert:”Orkut had the same problems with invites going out to Hotmail. Orkut responded that they had to work out an arrangement with Hotmail. About a month later several old invites arrived at Hotmail addresses. I suspect it has to do with an unknown source domain generating too many emails to Hotmail accounts in a short span and being picked up by Hotmail spam filters.”

And rumor has it, Yahoo sends the Gmail invite directly into the spam filters.