Is it possible your friend simply measured the length of the bow when it is strung, rather than finding the "AMO length" that should be printed on it somewhere?
I believe bow length is determined by measuring along the curves of the bow from nock to nock. If you strung a bow, though, and simply measured how long it is from tip to tip, you'd get a lower number.
A 58" AMO recurve could very well be called 53" strung, if you were just measuring straight, tip to tip.
Maybe not, but just a thought...