In the MIUI firmware, the built-in memory has ceased to be detected. How to recover?

Question

Android

Hello. Samsung SHW-M250L phone (Korean Galaxy SII CDMA standard) was flashed with MIUI firmware (v4 3.2.22). Everything worked great, except that the phone stopped seeing the built-in memory of 11 GB.
It turns out a FAT32 partition of exactly 1 GB in size /mnt/sdcard and a flash drive /mnt/sdcard/external_sd. When connected to a computer, only these two sections also come out. In the "About phone" section, it shows 16 GB in total (I think this is due to the fact that the i9100 was taken as the basis, in the M250L the internal memory is ~ 11 GB), and 1.96 GB is available. I changed it to stock firmware, and the partition reappeared, and with untouched files.
I returned MIUI again, there is no partition again. If I understand correctly, then MIUI simply does not mount this partition? Googled, came to the conclusion that emmc is not mounted. But in the root file system, this folder is missing (I searched through Total Commander) in subdirectories too. Installed Airdroid, opened the system partition on the computer, it's not there either. Now I don’t understand what to do, the section is there, but for some reason it is not visible.
Tell me, please, what to do, how to find and mount the missing partition? Thank you.

Answer 1

miui.su/panatseya-ot-bespamyatstva --- can this help?