Source file protection

[sutirtha]

Hello, everyone,
I have a situation!!
The buyer ordered a large banner with the source file. I made the delivery print ready jpeg+ mockup with the merged low-res source file because of source file upload limitation (150mb only)
The buyer happy with the design and asked the revisions to the high-res layered source file.
I assured the buyer after completion the order I will send the heavy layered file (approx1.8gb) via wetransfer file sharing method and also assured if not getting the original layered source file you may chance to cancel the order.
However, I upload the layered source file with password protected compressed rar file and deliver the download link with assurance provide password after completing the order.
I wanted to protect my source file because once I handed over I can’t get them back.
I had a bad experience with another buyers who took the source file and then canceled their order and walked away with free a design.
I noticed that source file is not protected by a watermark. So how I should deal with this situation?
Please help!!!
Thank you.