Rolling back

[calvin]

Hi all,

Here is my situation:

There was a tip in the main repo, and I had a clone. I made some changes 
to the local, committed, and I pulled the tip from the server. I merged 
it with local, updated, committed again and pushed to the main repo. 
However, later on I found out that I accidentally removed some important 
files when "merging, updating" period. I tried to use "hg revert", "hg 
rollback" but nothing worked (I reckon I used incorrectly) my local repo 
is messed up - have some missing files.

Is there any way to rollback to a moment before merging/updating process?

Cheers,

Calvin