Some data is lost when disconnected

My character just finished toto-rak dungeon, click on exit and suddenly got disconnected (black screen) last night. I have tried to log back in but unable to because 'world is full' or 'unable to fetch JP server'. Today I tried to login again for few hours and got the same error message. However I noticed that my level is back to lvl 27 when I supposed to be level 28 because I levelled inside the dungeon. The exp level shows the level that I have before I entered the dungeon. It seems to me the data during my time in the dungeon is lost. Please advise.

Was an emergency maintenance running at that time? Servers usually tend to roll back their database when they're performing such maintenances, that's why they encourage people to log out while they do it.

No, there was no emergency maintenance during that time.

I wouldn't do anything till you actually log in. I have experienced the same thing but once I logged in I saw that I had not lost any progress.

Something must have happened to your character on the server in and was corrupted. The server just reverted your character to the safest save state. It sucks but rarely it does happen in mmo's.

It's exactly like what you said. Once I login, all the data is back.