Not had this happen to me ever on any t mobile rom, I know the international roms can wipe your internal when flashing them but I dunno why any rom would wipe your internal sdcard on a reboot. I keep all my roms, kernels, themes, etc on external sdcard tho just because I have more room there and just use internal for apps.
Which rom/kernel were you on when this happened?
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Current Device: T-Mobile Note 3 (SM-N900T)
Sprint Note 2 (L900) - Hanging on to
Sprint Galaxy S2 - Sold
T-Mobile G2X (P-999) - Sold
T-Mobile Mytouch4G - Sold
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