Not sure if anyone else found a fix to this yet, but as I was having the same problem and couldn't find help on how to fix I thought I'd share how I resolved it in case it helps anyone...
I logged into Flow (https://unitedkingdom.flow.microsoft.com or us.flow.microsoft.com, or whatever is the correct country for you), ensured I selected the correct environment, clicked on 'Solutions' and then opened the 'Default Solution'. I filtered the selection to 'Flows' (top right filter options) and found it listed here.
It was still owned by my user account, but didn't appear under My Flows or anywhere else.
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