I have rated a theme(Listing Pro) 1 star because the theme is terrible and the support is pathetic. To my surprise my review is taken off! why does this happen?
I see the theme has an overall good review because only good reviews are kept in the system and bad reviews are taken out. This is not good for someone who is looking to buy the theme as the reviews doesn’t truly represent the theme!
Probably the author considered that the review is not right and contacted support and the support theme removed it based on his arguments.
I had many unfair ratings that were removed by the support theme, I am not saying that your review is not right but in some cases, reviews are a mess, in my case, many clients did not even bother to read a few lines in the documentation, they jumped quickly and rated 1 star…
This is strange…The theme guys break the theme…Buyer suffers…they take days resolve and then get the one star removed behind the scene! how fair is that!
No wonder how they have fudged 4.84 star for their theme!
Assuming this is the theme you speak of?
Then I disagree that negative reviews would be removed all the time.
If you were rude, or the author had shown they had done their best to resolve your issues within a reasonable time (for example not 5 minutes after people think they should get an answer) then perhaps that explains why your review comments might have been challenged.
I’m only saying my friend as I do not be in possession of full facts 
You should write about this Submit a request – Envato Market Help Center , Envato support theme is on point, if your review is correct they will add it back.