I've been in situations where my friends are invited to an event and they'll get an invitation electronically, or physically. Sometimes I won't get one even though my friends have gotten one, and I know the host very well. It seems like I should have an invitation, and there may have been a mistake. Further, should I show up at the event, the host may not want me there, and it would ruin the scene.
Obviously, asking the host directly puts them on the spot, and makes them uncomfortable should there be no mistake, and they don't want me there.
Given that I am by myself (I can't have the aid of a friend), how do I ask if I have an invitation or not to an event without putting the host on the spot?