"Fill" In Dynamic-Q Bugged?

I was attempting to play with a friend and his friend. We queue as a 3-man. Roles selected:

1. Friend of friend. Mid/Jung
2. Me. Fill
3. My friend. Top/Jung

We waited almost 15 minutes without a single queue pop. Leader takes us out of queue and I switch roles. Role list NOW:

1. FoF. Mid/Jung
2. Me. Supp/ADC
3. My friend. Top/Jung

This queue took only like 2 minutes before we found a match. What's going on?