While I definitely agree that the AcadDoc.LSP route is a "better" way of going about loading custom lisps (or perhaps adding a MNL file to your CUI). This being one of the reasons. Another being the fact that it's then a simple file copy to install the same into another computer and/or new version of ACad. If you do run into such issues you need to edit registry:
The StartupSuite auto-loads are saved in each profile of each version of ACad separately. E.g. for the "unnamed" profile in Vanilla 2016 ACad they're under:
HKEY_CURRENT_USER\Software\Autodesk\AutoCAD\R20.1\ACAD-F001:409\Profiles\<<Unnamed Profile>>\Dialogs\Appload\Startup
You should be able to delete them using the regedit program (in Windows' Start menu start typing regedit and then click the regedit when found, you might need to answer Yes for admin rights).