Besides checking whether electrum is properly connected to a server
that error message is coming from a server. in other words you connect properly then send the raw tx and then the server verifies your tx and sends back a reply. in this case the reply was a rejected reply and the reason is he is trying to spend this tx which doesn't exist:
6ac272bac931a4e5201767dd9cbcc2ce557300544788e9b93bf9e36d6ce1e68a
0100000001 8ae6e16c6de3f93bb9e9884754007355cec2bc9cdd671720e5a431c9ba72c26a 01000000fdfd00....
as you said in the end it is probably stored locally. or maybe it was an unconfirmed received tx which got double spent.