Oh please, get over it.
This dude enquiring about employment elsewhere is no different from millions of other kids starting out in their careers. All bright eyed and bushy tailed, wondering where their new path will lead. Fact is, you can't make a move without experience. Typically 3 years. So you'll have a guy for three years before he can start looking around.
Would you feel a little used?
Has it never happened that you go through the process of training someone only for the company to transfer said person straight after validation????
Swings and round-a-bouts people. It's the nature of the beast. Damn silly trying to hunt down individuals.