Have you been to Fuerteventura on holiday or maybe live there? Is your wife's name Tiina? Were you married on the 18th of June 1991? Did you lose your wedding ring in the sand at a beach bar? The bar man said you spoke Spanish with an accent and thought you were from Finland? If so...I have your ring!!!!
Please email me with a description of your ring and the name of the bar and town in Fuerteventura and I will send it to you. I live in Scotland.
With a population of about 5,000,000, how many Tiinas probably got married on that particular day? I'm guessing normally just one.
The Central Population Registry could easily identify and possibly notify this person if you found a cooperative bureaucrat.
They can't and won't give you that information, naturally, but for something as sentimentally important as a wedding ring, they might notify the person and pass along your contact information. They won't have the person's email but they should normally have a valid postal mail address for the person. At least it doesn't hurt to try.
The public point of contact for the Registery is kirjaamo at vrk dot fi.
Why don't you send them what you posted here and see if anything comes of it. I know that for some people it would be devastating to lose something like that. (Then again in Daniel Martin, a character deliberately buries her ring in the sands of Egypt. I have trouble picturing how you accidentally lose a ring in the sand, but who knows?)