Can't find a way to automatically redownload them to my Lightroom catalog on my new macbook. Is there a way to do this?
The answer is No.Your synced images on your iPad are just the smart previews of your original images and cannot be recovered or treated as a backup copy of your images.
Collections containing those images are only present on our servers so long as they are being synced there by your desktop. Lightroom Mobile does not act as storage container for your files.
Thanks for your help Akash!
That's too bad... I still have the majority of my shooting on my SD card but that means the beginning of my trip is lost.
Next time I'll make some backups elsewhere, lesson learned!
What you can do is download smart preview -sized JPEGs from Lightroom Web. So on another computer, you use a browser to log into Lr Web, then click the download button. One at a time, yuck. Alternatively, on your iPad you could email yourself the missing photos. Again, you'll get large JPEGs but not full-sized images.
"I still have the majority of my shooting on my SD card but that means the beginning of my trip is lost."
Those from the beginning might still be there. Have a look at ImageRescue or other programs that can recover deleted files from an SD card.