This is the visual bug ( http://imgur.com/zJjCCWU ). Every time I view a different mercenary before a match this will show up while I am playing. I have to change from full screen to window then back for it too be removed.
Last match I was lagging a lot and while I did play both rounds of the stop watch it showed that I earned zero exp and gold. ( http://imgur.com/Lyzq9wj )