Looking into it now for you
Theme won't save

I just ran into this same problem. However, my issue goes further. When I tried to search for the theme that I had saved, I found a theme whose author was "whirlwind2011," and the theme was titled "whirlwind2011's space ch...". However, I am not the author of this theme, so I don't know why I would be "credited" with it. I would like to recover the theme that I actually attempted to save. I would appreciate any help. Thanks!

If you click on Copy by that theme, then change the name of it to something else, you can save it as your own then.

Well, I don't want to save the space theme. I was designing a completely different theme, and now I cannot find it. I attempted to save it under the name "Final Fantasy." How might I find that one? I saw how to search by author, but not by theme title. Thanks!

It doesn't look like it saved. If it did, it'd be under Account/Themes/My Themes
You're not showing as having any saved though.

That is the main problem. I clicked "Save Theme," but it didn't save; instead, I was redirected to a blank Create a New Theme page. I must admit, I was disappointed. I had been working on that theme for a couple hours getting the colors just right. How might I avoid this (bug?) in the future?

It may have been due to the length of time the page was open, and it timed out :(
Try creating the theme, then as you're editing it, try clicking on Save theme every 20 minutes so that way if it does show a white page, you haven't lost the whole theme as you've been previously saving it.

Ah, that must be it. I guess I was concerned that if I saved it, it would have been considered finalized, and so I didn't want to click Save until I was finished. I'll give that a try. Thanks!

Hm. Unfortunately, I just tried your suggestion, and it didn't appear to work. I started to create a theme, modified just a few features, and then saved after a few minutes. I was still taken to a blank form, and my theme wasn't saved anywhere. Any other ideas?

Strange! I will try it again, then.
When you click Save, does the theme show up right away, or does it take you to a blank form? Also, are you then able to find it in the list of themes? I could not get it to do either of those things.

yes it did for me. If i chose a color for background (as example) it showed on the page as i was creating the theme. Then once saved it showed on all pages until i change it to something else.

Yes. I finally got it to work, after two more attempts. The first time, I made about half the changes and then saved, which took somewhere around 5 minutes. But when I saved, it vanished. I tried the second time, made about two or three changes and saved after about 1 minute. It finally saved successfully. The page seems to time-out very quickly for me.

I am encountering two new issues with themes. First, when I try to simply edit a theme, it will automatically switch over and use the theme. However, I want to use one theme for my account, and a different one for a group I started. Whenever I edit the group's theme, it "takes over" my specific account.
Second, I tried to load a custom logo that I just finished designing, and the logo won't change to the new one. I made sure that it's 150 x 60 pixels, and it is saved as a jpeg. The problem can't be the page timing out, because I'm clicking Save Theme within a few seconds (since the logo is the only change I'm making to this theme right now).
I tried making a theme today. After I clicked Save Theme, it brought me back to the same Chess.com theme, and deleted all of my work. (It did not save my theme either). I also checked the My Themes section and there wasn't any theme. Is anyone else having this problem or is it just me?