What is the data / content retention duration on lemmy.ml?

Hello, I noticed some of my early posts (less than a year ago) disappeared. I did not receive notification about the removal. Hence I suppose it could be due to one of those:

• the instance hosting the community got defederated
• the community I posted in was removed
• there is some automatic cleanup job of old posts on Lemmy.ml

This is not mentioned in Lemmy.ml's presentation section. Does this instance implement pruning? (if so; what is the retention duration?) Is it possible to check the retention policy of a Lemmy instance?