Good afternoon HeathJ,
And fingers crossed thank you!
I lost a Sony XZ2 down Vesper pot around the end of November.
If it was lost where I think it was, you will likely have found it at the bottom of the second pitch, it's roughly 65*120mm dims and is a silver colour, is in a red silicone case which covers the back and sides with a glass screen protector over the front.
The lock screen image is of a caver stood on the left hand side of the main passage of "Grot Favot" (huge pentagonal shaped passage).
If the description above matches what you have found, please call me on 07773 021 874 to arrange its return!
Kind regards
Rob