If your saddle was pretty new, did not yet have any treatment from Proofide (or similar) and one side got damp, I would not be surprised if that side was more indented.
If the saddle feels fine when you ride it, I would not worry about it.
I always put a rain cover over my saddle at night to prevent it from getting wet in the dew.
I did some leather tooling when I was in scouts as a kid. From that I know that wet leather takes a new shape quite easily.
And from that I know that if you apply any treatment to the leather, that slows its ability to take a new shape, so I never apply Proofide until a new saddle has started to take the shape I want it to take. I also make sure that a new untreated saddle is never exposed to rain.
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I find some new Brooks saddles are hard as a rock when new, especially the Brooks Pro. I put a new Pro on my newest touring bike a couple months ago. I do not recall where I heard this, but someone suggested that one way to accelerate break in on a new Brooks is to dampen teh leather directly under the sit bones area and take a short ride. I did that, I placed some small pieces of paper toweling that was soaked in water on the underside of a Brooks at those sit bone areas to let the leather get moist in those two spots. Then went for a short ride. That accelerated break in. My break in method before this saddle was to soak the entire saddle in cold water for about 10 to 15 seconds before a short ride. Note that I said seconds, not minutes, you only want the leather to get slightly damp, not wet. After the paper towel method, I still wanted to accelerate things a bit more, so I did a 10 second soak and a short ride. Then let the saddle dry out for several days. At this point it was about 70 percent to where I wanted the shape to be so I decided to quit using water at this point. I applied a layer of Proofide to top and bottom. And started riding the bike like I normally do around home. I did a 5 day bike tour about a month later so I put another layer of Proofide on top and bottom before that trip. At the start of the trip I had 233 miles (~375 km) on the saddle and it worked great for all five days. We had some rain on that trip, but with a leather saddle I am always careful to use a rain cover on it when it is wet. That saddle now is very comfortable, it has about 600 miles (~900 km) on it.