In Chicago, a VERY tenant friendly area, if a tenant expresses that they have vacated the property, it is considered landlord possession at that point.

If property managers and landlords have locks, isn't it very easy for them to steal tenant possessions?

The people asked me to help and the only thing I can think of is adverse possession.

I do agree in the wisdom of inspecting the homes as some of them very well could end up in the park owner's possession. 

It looks like you can dispose of the possessions after 10 days if you do not hear back.Section 1.

I changed the locks and took possession myself on the grounds that it was vacant and therefore the prior owner was not in possession.

Then after 3 years of possession, the title will quiet and then the title can be insured upon, or you can look to the previous owner and see if they will sign over a quick claim deed for a couple hundred bucks.

This can be plaintiff or defendant in business disputes (partnership breakups), consumer DTPA claims, breach of contract, specific performance, probate (title issues), adverse possession/trespass to try title (quiet title actions for breaks in the chain of title), or suit for declaratory judgement (interpreting a contract or boundary).I am admitted to all TX state courts, and the Federal District Court for the Southern District of Texas. 

(See Idaho Code 63-1005 – One-year possession under tax deed conclusive as to regularity of proceedings.)That makes it sound like you have to hold on to the QCD for a year to clear up any potential issues with it, but I haven't seen an indication of that anywhere else - including Idaho Code 63-1005 mentioned there.

In my opinion, she has not legally surrendered her possession of the rental unit if she has not returned the keys.