I already checked the Input in the environment and I can only see that there is actually audio signal coming from the channel strip
Did you check the actually Sequencer Input (on the Click & Ports Layer) in the Environment? The Mixer Layer with the Channel Strip pretty much shows the same what you see in Logic's Mixer Window. You should look for the mysterious MIDI source.
Do you see any input in the Monitor Object coming from the Physical Input going to the Sequencer Input?
Check your Audio MIDI Setup app, All those Devices (even IAC, BLuethooth and Network are feeding into Logic

When you talk about the little bulb, I guess you mean the LED in the Control Bar Display. Set it to Custom so you can see a more detailed MIDI Input and Output reading. As far as I know this reads the MIDI input on the Physical Input, any external MIDI Devices or the Musical Typing Keyboard. I don't think any internal MIDI signal routing (if it is generated by a Software Synth) should show up there

Also, do you have the MIDI Monitor app? This is a free utility that shows any MIDI signal going through your computer. It might help you to check on any rouge signals.
http://www.snoize.com/MIDIMonitor/
Hope that helps (this time)
Edgar Rothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
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