On the Mac, I found the keystore file path, password, key alias and key password in an earlier log report before I updated Android Studio.
I launched the Console utility and scrolled down to ~/Library/Logs -> AndroidStudioBeta ->idea.log.1 (or any old log number)
Then I searched for “android.injected.signing.store” and found this from an earlier date:
-Pandroid.injected.signing.store.file=/Users/myuserid/AndroidStudioProjects/keystore/keystore.jks,
-Pandroid.injected.signing.store.password=mystorepassword,
-Pandroid.injected.signing.key.alias=myandroidkey,
-Pandroid.injected.signing.key.password=mykeypassword,
On Windows
you can find your lost key password in below path
Project\.gradle\2.14.1\taskArtifacts\taskArtifacts.bin
or ..taskHistory\taskHistory.bin
open the file using appropriate tools e.g. NotePad++ and search with the part of the password that you remember. You will find it definitely. Else, try searching with this string “signingConfig.storePassword”.
Note: I have experienced the same and i am able to find it. In case if you didn’t find may be you cleared all the cache and temp files.