I started using Bitcoin Core and transferred coins to this wallet. When synchronization got to the point where the coins showed up in the wallet I sent them on to an Electrum wallet, although Core had still not fully synchronized.
The Electrum incoming transaction then expired before the Core wallet had fully synchronized. Now Bitcoin Core has finished synchronization and shows the outgoing transaction and empty balance although the Electrum wallet never received the transaction.
Are these bitcoins lost or is then anyway to reclaim them?