Loose trunk lock cylinder

I'm gonna ask the obvious.....
Did you feel on the back side for the retainer spring clip that holds it in place?
If it is not there you can find one here: https://www.yearone.com/Product/chrysler-a-body/kt3
If the gaskets are missing, that will possibly make it loose as well: https://www.yearone.com/Product/chrysler-a-body/fd772r
Or if all else fails, you could buy a complete replacement unit: https://www.yearone.com/Product/chrysler-a-body/tl1

Hope this helps