I began to air up the tire and the entire plug fell out!

Not just the top(needle) or the insert(screw-out) but the entire stem,I had thought the stem was an integral part to an inter tube,affixed to the system as one piece,I have found out differently!

Any ideas as to how to fix this,I really don't want to be cruising at top speeds(30-35 MPH)and have this happen!