If you are lucky there is still a .acsm file in your downloads directory.
Double-click that and it should redownload from open library.
If double-click does not work, dragdrop the file from explorer onto an open ADE window.
No, I keep my downloads empty out of habit. :/ Is there any other solution?
Maybe, just guessing ...
1) Go to the OpenLibrary website and try to download it again. That may work; I'm not sure exactly how OpenLibrary works. I'm pretty sure it would work from my local library.
2) Go to the OpenLibrary website and try to borrow it again. That may work if there are multiple copies available for loan.
Your current loan will expire automatically when its time is up.