[KneelBeforeZod]

doesn't the offender have to leave the store with the stolen merchandise

no!

[alisasny]

How do you prosecute if the merchandise never left store?

Frankly I find it a rare day that a shoplifter is actually arrested and convicted.

[Chad Fairbanks]

Yes!

If they havn't left the store, there is, technically, no theft and the odds of ever getting a conviction are pretty damned slim (except for in Arizona, apparently)...