This doesn't answer your question but in W10 (if you have it enabled) Winkey+V brings up your clipboard history.
yes. I'm totally lost without ditto. And I've never experienced any trouble pasting anywhere.
But did you know that even Windows 10 has it's own clipboard history built in? I'll stick to ditto, though...
Did you already save the new version of the file? What I would have done is save the project under a new name. The old file would have had whatever was in the project the last time you saved it--hopefully pre-delete. But, it sounds like you might be beyond that.
If you'd copied the entirely of those 10,000 words (ie Ctrl+c), and if you've set up Clipboard, you may be able to restore them from your Windows clipboard history: https://support.microsoft.com/en-us/help/4028529/windows-10-clipboard
AutoHotKey as suggested is probably the most direct answer, but you could also use the multi-item clipboard built into Windows. Just use win+v instead of ctrl+v, and pin your word to the top.