Just want to share our story so that travellers are aware.
Unfortunately we were one of the victim.
It happened in Venice train station (Santa Lucia), after we boarded the train to Rome.
When we were trying to sort out the luggage (putting them on the rack), two teenage girls insisted to help. They insisted so many times that we finally gave in (guess we were just too tired with the luggage and lost our cautiousness), while the older girl was helping out, the younger girl opened our shoulder bag (wearing at our chest) and took the coin pouch out.
We found out a minute later, but they fled away already. Luckily we lost only little money as we put the big bills in our money belt. Should they have more time, they would have got our iphones from the waist bag too.
Afterwards while we were searching search for our empty coin bag (could not found it) we found another empty wallet on the floor (with no money, but passport and credit card were still there); probably was another victim from these two girls. We guess that they worked their way from the front of the train towards the end (we were at the end).
When we rethink the incident, we realized that those two girls had an eye on us from the minute we boarded the train; probably because we have quite some luggages (two persons with two medium size luggage and one carry on).
Advice: Don't worry about storing your luggage until the train actually moves. Watch your belongs whenever the train stop. Thefts probably use the really short period of time when the train stop at the station to do their business.
Feel sorry for those two young girls too...for becoming professional theft at their ages. They should be studying, having fun with schoolmates instead