Hey, I'm not sure how to load the game from within Splore, but if you want to load the game from within pico 8, you can just drag and drop the "p8.png" file into pico 8. Does that work for you?
It works for Windows and Linux desktops where dragging and dropping is functionally possible, but not for raspi, where splore is launched by a frontend like Emulationstation (common for raspi handheld consoles, arcade cabinets, etc). When I add the file to the /carts dir, it doesn't appear in the File menu in splore either. And, when I try to manually load the .png from the commandline, PICO-8 says "could not load putrid_s4nd.p8.png"
Hmm that's strange, I'm able to use "load putrid_s4nd.p8.png" from the pico 8 command line, at least on windows.
Does it work if you re-save the p8.png as a regular .p8 file (by loading it in pico 8 and calling 'save' again on windows or linux, wherever it currently works for you) and then pass that new .p8 file to your raspi?