APFS encrypted volume on external HD

I fear I know the answer to this before asking, but I'll ask anyway...

I have an external USB HD that I use for extra media storage, and the APFS volume is encrypted. A while back, I changed the password on it. However, I apparently didn't make note of what I changed it to, doubtless thinking (foolishly) that I would remember. But it's been a few months since I've used it, and now I don't remember what I changed it to. I've tried every basis for a password that I can imagine I might have used, with no luck (which actually makes me fear that perhaps I made a typo when setting the new password).

At any rate, I don't have the password, apparently. Is there anything I can do to rescue the data on that volume, or is it simply gone forever? Thanks!