Some of the addresses involved in your transaction today, were obviously funded AFTER the BitcoinGold fork... as they show 0 transactions on BTGExplorer.com
The addresses used in your transaction today had the following BTG:
1PW8EwnZTtZfhoiKSTN1wmetWzPNgn1gbH - 0.45894194 BTG
1Jm36Wt1BcMfpFwqDCT2P96wWVYpoiSHmm - 0.02017051 BTG
1M1coNNn1f4EQUThhw2cyrU6Cf5h72gw8L - 0.09580369 BTG
1M1coNNn1f4EQUThhw2cyrU6Cf5h72gw8L - dupe
1MRtrnof7bwNajPxZeSCZQxLrLy8yRbHwh - EMPTY
1aaqrxoZCHQbtZ9tjn1qLMwBCeXuZxPT1 - 0.00029256 BTG
1KsY6kGRuq68hbgBmwHgej3EQVEsaLBSLm - EMPTY
I suspect that what has happened, is that the BTC addresses that actually had coins BEFORE the fork (and now have BTG), were already used in your BTC withdrawal transactions AFTER the fork... so your BTC transaction today, was using different addresses/UTXOs than what existed in your wallet when the fork happened.
You will need to look through ALL your BTC addresses from Electrum ("View - Show Addresses")... and find ones that have a "TX" value greater than 0 (This means they have received coins at some point in time). Then check each one on
http://btgexplorer.com to find the ones that actually still have BTG balance.