kicad issue with schematic open message

hi all, I have kicad installed on slack 14.2 64bit. I have an issue in that it doesn't let me open a schematic because it says it is already open. I have tried deleting all files in the project folder (I had only just started anyway), and it still thinks the schematic is open even though the schematic file is no longer there.
Obviously it is keeping track of it somewhere else, but doing Code:ls -al ~/ doesn't show any obvious hidden kicad files or directories where such info may be stored. looking in kicad itself refers to a ~/kicad directory, but as one doesn't exist, that doesn;t help.
any clues as to where to look to clear this fake "already open" issue? thanks.