you can find your lost key password in below path
Project\.gradle\2.14.1\taskArtifacts\taskArtifacts.bin
open the file 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.