If you look at the changes Log, you can see when merges were Completed. On that change entry, you can select the link for the 'merged away' profile, which will put you into that profile's change Log. At that point, select the Edit data on that last entry and you can see what was in the biography of that profile at the time of the merge. You can also see the parents, but not necessarily any other 'data' information or relationships.
If the profile has been merged a few times, you may have to go into several merges to find the one that you are looking for. If you know the wikitree ID of the profile that was merged away, you can revise the url of any profile's Changes Log url to be the Changes Log of another profile, but be careful that you don't select the initial created entry because it will return you to the new merged profile.
