Sorry, but sometimes I get drowned with questions.
A case like this, when cold, is really hard for the police to prove, because the goods may have been disbursed to other locations by now. However, it's well within the statute of limitations.
Your other option would be to sue for trespass and conversion. But, you would have to prove that the neighbors came in and took things without your consent. Once again, very difficult to prove after all this time has passed.
You could sue the real estate agent for negligence or breach of fiduciary, for not telling you that the neighbors had a key to the property. That actually would be your best method of getting damages, if you could prove that the agent knew and forgot to tell you. You could also sue the seller for negligence -- also probably a better cause of action, because the seller must have known that the neighbors had keys.
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