Can't Assign Flex Player

I need some help here. I traded the person on my flex (an NA player so not locked) with an EU player. Now on my roster screen it shows me as having no flex player and when I try to assign a player I get the error "The exchange would leave your team with an invalid starting roster, with too many players at one position." I want to assign one of my other players (not the guy I drafted) to the position for the week. In the Add/Drop screen it shows him as my flex, but not on my roster. I don't want to lose this week just because I don't have a flex player. Thanks!