World Editor: Why do object ID numbers change?

Why do the object numbers for the same exact object change, each time I exit the game and then come back in?

I have some floating road signs in a level I created, that I'd like to put back where they belong-- comparing my level with the default map. To confirm they're even the same road signs, I'm going to have to make a positive match. I wanted to do this my ID #, but this is next to impossible if the same road sign changes numbers in my level.

First time in, a yield sign was ID #56139. Second time in, #18852. Third time in just now, #36879. The idea of an ID number should be to uniquely identify the same object, no matter how many times I exit the editor, exit the game, and then come back in.

I find this very troubling. Why does it do this?

EDIT : I have since solved the problem. While the number change problem never got solved, an overall hunch as to where the road signs belonged, emerged. I kept going back and forth between the default map and my map, and went to different roads until I finally found the signs that were present in the default but absent in mine. A yield sign, a T-intersection sign, and a left-S-curve sign.

It was a tedious process, but it's done. But if anyone knows why objects will sometimes change ID numbers in the world editor (the F11 one, not the F10 one)… I'd still like to know. Thanks.

 

Nadeox, Okay, thanks for letting me know that. So use names instead of numbers... got it. That was easy for the boulder that was hanging in mid air. It was called "Rock_143". However, all the road signs were named "TSStatic". Rows and rows of the same exact thing, is why I was hoping I could go by unique number identifiers, but oh well, at least the problem's been taken care of.