I was browsing a book store within the past five years and read a blurb of a book on the SF section. I do not remember the author or title, but the plot was something along the lines of that in the question, and the book was written from the perspective of one of the investigators/scientists/military folk involved in the discovery. If I recall correctly, a large shiny metallic hand was unearthed, but the hand was postulated to be the tip. I think the book progressed as more of the thing was dug out.
I could be inaccurately remembering the blurb.
Anyway, I'd like to finally read it. If you can help me locate the title that'd be great.