Tomato blooms are disappearing.

Plants look great but some of my blooms are disappearing. It looks like someone cut them off with a knife...straight cuts. I check them every day. I haven't seen any worms or other pests. One stem had 5 or 6 blooms on it and 3 of the blooms are gone. At first I thought maybe it was a cutworm but I haven't seen any worms at all. Could it be a virus or something?