Just played a game with the prince where there only thing that happened when I played it was that an action disappeared.
Only available card to play with it should have been "Sea Chart", where as "Magpie" supply pile was empty.
Do you have a game number for that game? If not, could you send me your in-game name (maybe via direct message here), then I can have a look myself.
I have a screenshot...
Thanks for the screenshot, but in that situation that is what is supposed to happen.
Prince reads:
QuoteYou may set aside (on this) a non-Duration non-Command Action card **from your hand** costing up to $4.
At the start of each of your turns, play that card, leaving it set aside.
When you played Prince, you only had Treasure cards left in your hand (Silver, 2x Gold), so you could not set aside an Action card at all (let alone a non-Duration non-Command Action card costing up to $4). In this turn, you drew the Prince late, with only a Haggler in hand at that time, and since it costs $5, you also couldn't have played it with Prince. So on this turn, Prince couldn't do you any good, if you played it or not.