Some pax dont take baggage to the check-in desks which is usually taken off them at the gate. Also, bags checked in that are out of size must be taken to the Out Of Gauge (Suit carriers / Brief cases). Some pax think that that dont have to do this. The list in endless, but some pax will try to do what they want.
The Hostie in this case should have taken all bags off pax on the flight. After all, with the additional security, all the check-in staff are trying to do is limit the delays caused by additional searching.
MAN airport have worked hard to try and make the additional security arrangements enforced by the DTLR workable. Give them a break. If these measrues were not but in place, long delays will still be an every day problem. Like it or lump it, these security issues are here to stay, we ALL have to work around them or the airlines will be fined large amounts of valuable cash.