A theory , because something similar happened me just the other day.
I was in a party and wanted to invite a friend. At the same time he invited me and we both replied to the message.
I ended up in no-man's land, and he ended up n the party from which I invited him, but I was no longer there.
The person who invited you also invited someone else. BY the time you go to the party, the person who invited you left.
It is a race condition.
Just a theory...