I lost my engagement ring. Considering everything that ring has gone through it was pretty anticlimatic...
I mean, I've worn it in factories (silver gets some really psychedelic colours when it gets some chemicals on it) I've worn it while swimming in lakes, rivers and oceans. Then I go and take it off before a sparring match and it slid along the dashboard of my car and went into the ventilation. Having it removed from there would cost more than the simple silver ring was worth. (I've never liked gold, I just think it's tacky and does not suit me. I rather have something that works against werewolves any day.)
Here is a tool that may help, unless your ring is Sterling or nearly 100% silver. Most likely though, it has some steel or metal in it that will allow a magnet to pick it up. These are available at auto repair parts stores, for less than $10 US, so about 8.00 Euros.
Also, before you go to the auto shop, if you have a vacuum cleaner with a nozzle or wand attachment, they make long skinny hoses with adaptors and mini tool tip sets for cleaning computers and such. You could pick a set up very cheaply and use that with a fresh filter bag or cleaned dirt cup to rescue your ring, if it is not magnetic sensitive.
These are usually available at computer stores and office supply stores' computer sections.