How do I find my missing photos?

Thanks zinacef! Do I wait for the upload to finish first and choose Download and keep original or I'll have to wait for the optimized photo option to finish? I'm getting confused with the process. Sorry.

Thanks eric. The thing is I used the optimised option intially and this is when the photos started to go missing and was not even in icloud. So idk what's going on. I checked the uploaded photos and compare it with the remaining photos on my phone but it doesnt some up. There's a huge difference and again I cant find any of the photo that went missing. Is there a different step on how to retrieve the photos when I chose the optimised option or this should show in icloud automatically?

So far i tried to turn off my icloud photo library and turn it back on again and it says that there's about 4100+ photos to be uploaded wherein when I compare the photos from my photo app it only shows 3800+ photos. I'm starting to regret uploading my photos in icloud as this is the only time that this has happened. I checked the other albums I have and there's also few photos missing and the others don't. What's going on. :(

And if ever it doesnt finish downloading does this affect the progress or this is okay?

I dint see any deleted album as the album itself is still in my phone, only a few pictures went missing which is weird. I am doing this using my phone and not from a computer.