Hello Taegujim,
I'd like to help make sure you're able to locate the missing Playlists on your iPhone, if possible. If you haven't had the chance, if you have not tried already, please Restart the iPhone. Does this help to resolve the issue?
Does the issue occur when you're using cellular data, Wi-Fi, or both? If you haven't had the chance, check that now.
If you continue to have the issue, please get back to me with the following information:
- Do you subscribe to Apple Music?
- Is iTunes Match enabled? Here's how to check: Subscribe to iTunes Match
- Does the issue happen with all music, or just specific albums, and/or artists?
Please get back to me with this information, and I'll do what I can to get you pointed in the right direction.
Cheers!