SourKraut said:
...at what point do LEO have an excuse to enter private property without a warrant?
Depends on how "enter" they go.
Into someone's house, they'd better have a very very good reason that they can explain to the judge.
Onto the parking lot of a business, probably don't need much reason at all.
And I'm not disputing that they were reasonable in stopping & asking me what I was doing.
But once I'd answered the question & provided them with the means to verify what I'd told them (about the owner's permission) I think it should have ended there (once they did actually verify I was telling the truth).
So:
The first 15min, reasonable.
The next 34h 45m, not reasonable.