Are there any signs in the parking area about the terms of parking there?
Signs or no, there very well may be implied waivers involved if you CHOOSE to park in their secured area.
While cops are most certainly not experts on the law, his stating to you that your recourse was to sue them, and they he could not force them to release your property until their terms were met may very well be correct.
PLEASE keep us posted.
So, when you refused to answer whether or not you were armed, how exactly did that go?