Lost Photos not in icloud or on phone

icloud appears to have removed photos from December 2024 through to September 2025, months & years before are all there as are all months after September 2025. I bought a new iphone 17 in October 2025 which synced all my photos from my old phone but now I seem to have lost 9 months worth of photos. Any ideas on how I can get them back? They are definitely not in the icloud - from what I can tell. Thanks for your help.