I've moved the thread.
What I was trying to explain is that it's not possible to delete a stock model in the first place, so there is no need to restore it in any way. If it was in the software to begin with, it will still be there now.
Maybe if you explain a little more about exactly what method you're using to find it, we'll be able to help. Screenshots are encouraged.
When all else fails, you can press Ctrl-F to bring up the Quick Load dialog and start typing part of the name of the vehicle or airport for which you're looking. That's actually the method I use 99% of the time because I'm usually wanting a specific thing, but it's not very useful for browsing if you want to take a look through the available models and see what grabs your interest that day.