Were these VFR or IFR ones, A&C, that got lost?
IFR ones, once ACKd, should not just get lost.
There is a difference
at the tower of your departure airport though. If you filed the FP through their flight plan filing terminal (or whatever facility they provide) they will see the whole flight plan including the supplementary info (life rafts etc). If you file via AFPEx, they don't get that extra stuff, and IME might wonder if the flight plan has also been sent to the destination etc.
Most UK GA airfields are not familiar with this stuff and it confuses the hell out of them. They are used to people filing flight plans by walking up the steps to their tower
Whereas Homebriefing probably (*) just send the whole
VFR FP to the departure aerodrome and let it deal with any subsequent distribution.... IFR ones, they send to Brussels.
(*) On one occassion, HB told me they send VFR flight plans to the dep, dest, and the FIS of any airspace in which you have specified a waypoint. However, later they denied this, saying they merely send them to the departure ARO, and have not responded to subsequent emails asking the same Q.