Texas has no such law against withholding funds from an employee for failing to return information, documents, etc. and the Texas Workforce Commission has nothing to do with it. There are restrictions, as there are in every state, as to the process for doing so, which funds can be tapped, and the process used for reacquiring property.
I don't know of any government or corporate entity that I have worked for or been associated with in Texas that issues equipment, policies manuals, etc. to employees that does not have a standardized form clearly stating the allowed usage and the terms for return of the material and what happens if they fail to do so. The employee must sign this document before receiving the equipment. You are correct that in some cases an employee may not refuse to sign the document but then they will no longer work for that firm and it is a non-issue.
You can actually file a claim for any found property in any state. The law in Texas even allows claiming an abandoned building in Texas although that has recently been vastly restricted. I have actually acquired a car through the process but not to actually drive the car (long legal story). But the process to do so is not trivial and is not free. I would think the time and money it would involve with a found phone would not be worth the effort. If you do not follow this process you have no legal right to the property.
Your boy meets girl analogy is nice and brief but I doubt any company is basing their policies on that scenario. If they are their board needs to start looking for new executives. They won't get to consider the scenario much longer anyway as states are beginning to require locks. Samsung actually volunteered to build a hardware lock switch but the cell carriers said they would not off a phone with that capability.