Excerpts from the rules for Monopoly Deal by Hasbro
THE CARDS IN MORE DETAIL
Steal a property from any other player and add it to your collection. You cannot steal a card from a full set of properties.
Can also be banked as money.
ON YOUR TURN
PLAY UP TO 3 CARDS from your hand, onto the table in front of you.
A. PUT MONEY/ACTION CARDS INTO YOUR OWN BANK
B. PUT DOWN PROPERTIES INTO YOUR OWN COLLECTION
Lay property cards down in front of you to build up your property sets.
(End of excerpts)
The rules clearly state that either of these actions mean that the cards must be played from from your hand onto the table in front of you.
So, either way, you must be able to place the stolen card in front of you, and not keep it in your hand. As long as the card ends up in your collection by the end of your turn, you can steal it.