Steps to reproduce: 1. Go to http://www.cs.hmc.edu/~jruderma/s/. 2. Type a bug number into the bugzilla form (the second form on the page) and press enter. 3. Wait for the bug to load (optional). 4. Hit the back button twice quickly. Result: back at my home page, but the form isn't filled out. 5. Type 'g' into the google form and press enter. 6. Press back. Result: the bugzilla form is now filled in with the bug number you typed in step two. The google query seems to have disappeared. 7. Type 'a' into the altavista form and press enter. 8. Press back. Result: the bugzilla and altavista forms are now filled in. The google search is still lost. This is a dataloss bug, mostly after step 4 (because most users won't figure out the workaround), but also after step 6. Happens in 2001 070604 on WinNT. Doesn't happen in 2001 0628, so it's a recent regression.
Ok, I figured out the pattern here. The problem isn't the redirect; it's that session history gets confused with regard to form-refilling when I press back or forward while going back or forward. That is, after (hitting back+back, forward+forward, forward+back, or back+forward) *quickly*, the resulting page will not have its form elements filled with the values they had before. Resummarizing from "form submission leads to redirect -> form data not remembered after hitting back" to "navigating session history quickly appears to lose form data".
This bug still exists in 2001 071304. It's also a problem on the branch.
See also bug 93413, Going Back while page was loading makes form fields disapear on previous page.
I'm marking this as a dupe of 93413, which seems to be the same problem (it might be a dupe of bug 41555, but that bug is a bit old and non-specific.), but has a easier reproduction summary. *** This bug has been marked as a duplicate of 93413 ***