Lost all my pictures

Hi I had made a post and never had any help so I wanted to make a more detailed explanation of my problem! 
I have had for Lightroom quite awhile and absolutely loved it but I was always worried when I got a new phone that something would get messed up an I would lose pictures, and I did! In October I got a new phone and at the place they did the thing to transfer everything over I had a Samsung s21 and got the new IPhone 15 but when I got into my account on Lightroom  on my new phone there was nothing! I have a subscription to Lightroom and so I waited because I thought maybe it'd take a bit, although eventually about 5,000 of my pictures from Lightroom started showing up I never got the rest! My brother signed into my account on a computer and sure enough my missing photos are there but they're not shown they are errors! I am very saddened if I can never get those back because a lot of them are with my loved ones and my whole time in high school, and considering I have a subscription to Lightroom I'm saddened that I lost all of them! If anyone can help in any way shape or form I would be so incredibly grateful, these pictures mean a ton to me I want to get them back more than anything! 

Can you elaborate on your set up and workflow so a member of the community can help you further?

Do you have a paid subscription with Adobe that includes Cloud Storage?

What hardware do you have (Computer and Mobile Devices)?

Which versions of Lightroom are you using on those devices?

How do you import the photos into Lightroom?