No expert I, Max, but it certainly sounds extremely unlikely. I believe that wood and horn were the common materials amongst the ancient civilisations of the Mediterranean, perhaps decorated with precious metals in ornate cases.

The epithet ~~~~~ no doubt referred to the outer decoration of the bow, as silver could not enter into the active part of its structure. That the Greek bow was commonly a composite, or at any rate a horn one, is evident from the epithet ~~~~~ , which is constantly applied to it by Homer. This word signifies the recurving peculiar to the horn bow when un strung, which is due to the horns regaining their natural shape, and it is best translated by the word reflex, which is the tech nical term describing a bow which, when unstrung, bends from the centre in the opposite direction to that in which it is drawn.

http://www.xs4all.nl/~marcelo/archery/library/books/badminton/docs/chapter04/chapter4_2.html