Chicharito took his goal tally for the season to 13 by netting twice against Wigan last Saturday.
And Ferguson insists that means the £6million United paid Mexican club Chivas de Guadalajara for his services was an absolute bargain.
He said: "We've done fantastically well. We've stolen him!''
But the Red Devils' boss revealed Hernandez's capture was not a lucky pick by his scouting network.
The Scot added: "It was quite a long process involved in bringing him here - and we prefer that. We analysed him and found out all about his background. Once we knew that, our scout Jim Lawlor stayed in Mexico and made sure we got the deal done.
"We got him across to England and sealed all the contracts. It was a good bit of business. It started in the December and we didn't get the deal done until May but we'd been watching him since November.
"The reports were getting better and better so Jim spent a month in Mexico watching him in different games, internationals and things like that.
"His international record is incredible. He is scoring at better than a goal every other game.''