If you get an ACK, it should be in the system.
Whether you will get into the airways system with an OCAS-IFR FP is another matter.
You can file an IFR FP from say Lydd to Bournemouth at FL040, via SAM or whatever. This goes to Eurocontrol allright. But if you try to call up London Control for an airways entry, they won't want to know. My very limited experience with this kind of stuff is that there is no way to elevate IFR-OCAS FPs into a proper airways flight.
But that is not the same thing as it getting lost.
Unless somebody at Eurocontrol looks at it, realises it is OCAS, and deletes it from the computer after the initial distribution?? Then, the departure+destination will have a copy but nobody enroute will know about you.
How exactly did it get "lost" i.e. who exactly told you they didn't have it?