little help please

Yesterday i brought some vinyl off amazon (neil young) i notice that any purchases are download straight away onto my ipad, so thought why not give it a listen. Plugged in to ipad into the NDX and proceeded to loss myself in the music (especially down by the river, great track but thats not the problem). The problem is this morning i went to put it on again but the ipad only seems to recognise track from itunes....and im not sure why?