I checked every place in code where planets can be deleted. Every place has various logs. I checked every log but didn`t found anything.
On three different test`s server we rolled back database from backup from 5,6,7 July (it took 40 min each) and we found that the Gate was present at 5 July, but missing at 6.
In one hand it is a good news - the problem was before Saturday`s server problem.
In other hand - we don`t know where the problem.
Also I checked every line of code of every developer added on 5 July. Still nothing.
I added extra log at the last step of planet`s deletion. So if it happens again I`ll know the cause.