Two workarounds....and I just tried them both and both work.
Workaround #1 - - When you're in Voice Memo, click on the specific file you want to hear through your bluetooth speaker. When you get the drop down, you'll see the trash can on your right, the "Edit" in the center, and the box with the arrow pointing up on the left. Click on that. You'll want to click on "add to Notes", which converts the voice memo to an m4a file. Go to Notes, click on the four square icon on the bottom left and you'll find the audio file. At that point, you can play the file through your bluetooth speaker.
Workaround #2 - - in Voice Memo, email the voice memo to yourself. Again it will convert to an m4a music file. Click on the music file in the email and it will play through your bluetooth speaker.
I just did it and BOTH worked.
It's an extra step, and yes, it stinks, but at least you can now play the file through your bluetooth speaker.