I have a HyperV server with a VM for a windows file share. I have a VHDX attached to the VM that has all the data for the file share. I needed to temporarily remove the VHDX disk, and upon clicking "Remove" it prompted me to create a checkpoint to avoid data loss:

I clicked "Create Checkpoint and Continue" and I have a checkpoint from that time.
After reattaching my VHDX file, I'm missing months of data. The latest file I have in there is from November 2022, but some folders are missing data going back a year. I'm very confused.
I am new to HyperV and clearly don't understand how checkpoints in Windows works. What did I do wrong and how can I prevent this in the future. Luckily I have a separate backup from 2 days ago but I want to know why this happened and how to not get myself into this situation again.
Looking at my virtual disk storage, I have a few MRT/RTC and AVHDX files from today, everything else is from November.

I use Veeam as a backup and thought it created checkpoints every time it ran a backup, but the last recovery checkpoint was from November 15th 2022. In the checkpoints list, I removed the disk at the 12:43PM checkpoint.

Did I truly lose the data or am I missing something?