Damage control measures for potentially lost or stolen mail?

I mailed some forms which had info like my name, address, SSN, signature (no legal documents specifically though) for work to a large business address over two weeks ago through USPS First Class to a place another place in the US too far away to simply drive and hand in. They should have arrived within a few days of sending but as of today they still haven't arrived as I've confirmed with the recipient.

While I realize mail can be late/delayed with the USPS I'm taking precautionary steps right now in case the worst happens. I also am well aware I screwed up by using First Class Mail (or hell, USPS) in the first place instead of a place like FedEx. I should have learned my lesson with Priority Mail but no mail was lost that time; they just never updated their confirmation page with that hence I went with First Class instead.

That post office has lost me as a customer, but that's in the past so gotta focus on what to do from here on.

It's very possible that my mail is just floating around the business's mailing center but I'm preparing for the worst until proven otherwise. Anything I can do right now in case my worst fears are realized?