Help with Spot Color Channels and exporting...

Hi! I am teaching myself how to do some design work as part of my job as a communications manager at a small non-profit. I was working on a postcard we plan to get printed and I wanted to ensure the PMS color would be preserved in it and would be easy to match at our commercial printer. I watched several videos and read several articles on using spot color channels, and just when I'm ready to do a victory lap that I figured it out, I notice my top layer of my image is gone when I export to print pdf. I know spot colors drown out the CMYK, so I selected, saved selection(s), and then clicked delete with the spot color channel selected to remove them from. In the photoshop document, it looks right, but when I go to export I lose a crucial layer. I am wondering if the issue is in my export settings (which I have been trying to understand best I can) or if I'm still missing a step in photoshop. Any advice would be appreciated!