Tenant can't be found to return Security Deposit

[Nathan Gesner]

Wyoming law states I must return the deposit within 30 days, or 15 days after receiving a forwarding address. If there are deductions due to cleaning or repairs, I have 60 days to return the remainders of the deposit.

I've sent mail to the last forwarding address, tried forwarding through the post office, tried contacting everyone listed on her application, etc. No luck and it's been well over a year. Am I required to keep and track her security deposit forever or is there some statute of limitations whereby she forfeits the right to the funds?

I understand the Wyoming law as it's written and explained above. But there's nothing in writing to address a tenant that can't be located. Do I need to keep it for eternity? What about the costs of accounting for it, maintaining an account, etc? At some point the tenant should forfeit and I'm wondering if anyone can show me law (not opinion) to support this?