International Institute of Cricket Umpiring & Scoring
He was only being helpful
"We all felt rather aggrieved when our number eleven, who is a fine bowler - but
a pretty hopeless batsman - played an unusually good defensive shot to their opening bowler,
who had been put back on to polish off the tail. The ball dropped down by our man's feet
and he very kindly picked it up and threw it back to the bowler. Someone appealed, and
the umpire gave our batsman out. It didn't seem like fair play to us."Thankfully this doesn't happen very often. But, once a batsman has played the ball, he should not make contact with it again with his bat or his person, unless in defence of his wicket, or with permission from the fielding side.
Incidentally, this unusual dismissal is now recorded as out - Obstructing the field.
Read more about Law 37.4 (Obstructing the field) at the MCC website