Oh I've done it myself, trawling through a parish register thinking to myself "these names seem awfully familiar" only to realise after a couple of hours that I had already searched it before, and I had actually made a note of it somewhere.....I'm sure I did....just can not, for the life of me remember where I actually filed it!

Some times though a second or third pair of independent eyes coming to the same conclusion is good, as it means we are all probably right!