Heist should be banned or modified for several reasons:

-Heisted cards do not count against hand total.
-cannot see what was heisted
-overpowered cards:

Grave Expectations - 1 mana to steal a hidden card at no discard cost

Triumphant Getaway - 4 mana to steal 2 hidden cards, then use any color to cast them and -2 to opponents if used

Grenzo - completely broken card with ability to cast 1 heisted card for free each turn, and heists upon entering battlefield AND each upkeep.

Other heist cards like Thieving Aven, Impetuous Lootmonger and Weave the Nightmare are more fair, with the exception that WtN should cost 1 extra to do both actions.

Grenzo and Triumphant Getaway should be banned altogether. Grave Expectations should either cost more mana or require a discard. Any heisted cards should count against hand total. And they should be visible. This would make it fun again.

This is by far the most frustrating, broken, overpowered mechanic in the Alchemy format and needs to be modified substantially.