Sorry i think i may have confused the situation - "relay" is a general term in this context. The starter "relay" nowadays is usually located within the starter motor casing, sometimes it can be remote but the clue is the massive cables that must attach to it. The diagram you posted indicates the "relay" is within the starter motor housing. Other names for this "relay" as used for electric starter applications are: "Solenoid" - "starter switch" - "starter contactor" - the reason for all these differences is that the "relay" may be combined with other functions like operating the starter mechanism.
To be definitive the only way to really test this is using two people.
1. Put everything back together as normal.
2. Wait for the incident to happen.
3. Place voltmeter (multimeter on 12DC range) - red probe held on starter small wire whilst its still connected (you may need to expose either the wire or get probe onto an exposed part of the terminal , there should only be one small wire. Place other probe on engine block.
4. Get helper to turn ignition key.
5. If you get 12V but no clicking, its the starter solenoid
6. If you dont get 12V its either the ignition switch or engine block earth or power to ignition switch upstream.
Whilst the above is as general as i can make it, a photo of the starter showing all attached wiring will help determine if the "relay" is within the starter housing or remote.
