Trashed engineer played again with Royal Carriage can gain twice

[Picon]

Game #968168 on frankfurt.

I played an Engineer and trashed her, to 3-pile the game.
Then I called Royal Carriage (twice). Each time I was able to "Trash" the Engineer and gain a second Estate.
This should not had happened, as the Engineer has a "if you do" clause.

In fact, Royal Carriage should not be able to be called at all, as the Engineer is NOT in play anymore!

Turn 18 - Picon
P plays an Engineer
P gains a Curse
P reacts with a Watchtower
P trashes a Curse
P trashes an Engineer
P gains a Curse
P reacts with a Watchtower
P trashes a Curse
P calls a Royal Carriage
P plays an Engineer again.
P gains 2 Estates
P calls a Royal Carriage
P plays an Engineer again.
P gains 2 Estates