"Are you getting into dark stuff?" She timidly asked throwing down the card she had just retracted from the sealed envelope as if it was an instrument of evil.

I who am old to cards but fairly new to magic, have been flipping out my wife with some neat little numbers. I don't know what name(s) this trick is called, but I 'thought it up" though I'm sure its been done in many incarnations, and have no idea who really discovered it.

Asked wife to take the deck, shuffle to hearts content, then deal out as many of the blue backed bike cards as she likes face down onto the table. "Don't worry about stacking them neatly" I told her. Eh-hem.

"Stop when you feel you've reached your card, I told her.

Okay, this one. She replied.

Are you sure?

Okay maybe a few more , she re-thought.

"This IS it."

You're sure?

YES!

I drop the sealed envelope onto the pile of cards. First we check her final card on top of her pile.

"9 of diamonds" she says.

I hand her the envelope...... Theres a red backed bike inside.......

(Cue the theramin)

The Envelope, Please from Magic for Dummies can be adapted to the handling you described.

For dummies or not, it killed again last night for a big group of folks.
Followed it up with card "Vanishing Card" (Trace Unseen). Wife wants to call a priest.

It is indeed a very good effect

You will also find the effect in Paul Daniels Adult Book of magic

Bobsolarimagic.com has a new double DVD set available and he has a very nice effect on it (as well as many others) predicting 3 cards using an ungimmicked coin envelope.