The platinum ring was finally recovered when her fiancé found it in a bird’s nest at the bottom of their garden.
Julia Boaler, 36, thought the £5,000 ring had been stolen when it vanished while she was taking a shower at home.
Miss Boaler and her partner Justin Laycock, who live in Gleadless, Sheffield, were baffled at how the pear-shaped diamond could have vanished.
Miss Boaler, project worker for homeless children, said: “I was heartbroken when my ring vanished and Justin was not best pleased either.
“I left it on the bathroom window ledge when I took a shower but it wasn’t there when I returned.
“I thought it must have fallen in the bathroom or even fell out of the window but it was a complete mystery.
“When Justin got home I told him what had happened and the pair of us searched everywhere.
“We ripped up the bathroom lino, pulled up floorboards and even took the panel off the bath thinking it must have somehow slipped through but still it was nowhere to be found.
“I tormented myself for months looking all over the house for it thinking that my mind must have been playing tricks on me.
“I repeatedly rummaged through drawers and lifted carpets and turned the car inside out.
“I even accused the window-cleaner of swiping it as the window was open, but he swore blind that he knew nothing and I no proof.
“We eventually gave up looking.
“A few years later we had to put the wedding off as I gave birth to our son Luis.
“Needing more space we found ourselves putting the house up for sale so I made Justin tidy up the garden and cut the trees back.
“He started to prune our big oak tree and noticed an old nest in the branches so he nipped up a ladder to have a look inside and found my missing ring.
“I was gobsmacked.
“The bird must have swooped down and nabbed it from the open window.
“It’s amazing the ring was still there but I’m so glad to get it back.”
Still engaged, the pair have now insured the ring and are planning to tie the knot in the very near future.