So are you using the dbconnect app? If so, I think you should be able to manage the inputs from that app (at least with version 1.x). If that doesn't work, then you can use btool to find where that configuration is on the file system. It will be under whichever app you were in when you created the input in Splunk Web. Something like:
[splunk home]/bin/splunk btool inputs list --debug
Side note, I do think that some versions of dbconnect break the data inputs page. So if you are using that app, review the release notes to see if that's what you're running into.