How do I disable a launchd service I no longer have the plist for?

I delete an app that had some service running through launchd. Now launchd complains all the time in the console for not being able to launch the service:

19/02/15 08:50:28,589 com.apple.xpc.launchd[1]: (com.sovapps.launchAtLoginHelper[16732]) Could not find and/or execute program specified by service: 149: Could not find a bundle of the given identifier through LaunchServices: com.sovapps.launchAtLoginHelper
19/02/15 08:50:28,589 com.apple.xpc.launchd[1]: (com.sovapps.launchAtLoginHelper) Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

Since I no longer have the plist file, I can’t simply unload the service. How do I make launchd forget about the service?