Metal detectors will work to find aluminum arrows to an extent. The detector should pick up the whole aluminum shaft and you should be able to draw a line right over where the arrows is, dig a bit, and get it.

If they are not bent beyond repair you can find them and reuse them.

I would suggest putting some kinda backdrop behind your shooting target (I assume that's what you were doing.)

A plywood board (if using carbons)...dirt mound...styrofoam block...something to stop your arrows, otherwise they are much harder to find.