I have two "spare" Ecolink Sensors: DW-ZWAVE2 /FCCID: XQC-DWZ1.
I took one, which I think was paired to to one of my other Z-Sticks and watched live logs while waving a magnet nearby. Saw the blinking LED to indicate it saw the magnet's movement. Nothing in the log, indicating it's not paired to my "production" network. In other words, an ideal device to mimic your situation, because I'll have to Exclude it and then Include it.
Just to make sure, I put Hubitat into Discovery and did the pairing dance. Nothing. Perfect, it is paired to something else!!
Now I can start the real test.
I removed the Ecolink cover, pulled the battery, waited 5 seconds... put Hubitat into ZWave exclude... Performed the Ecolink Include/Exclude dance.. nothing noticeable to confirm Exclude.
Removed the cover again, pulled the battery again, waited 5 seconds, again...
Performed the Ecolink Include/Exclude dance.. nothing noticeable to confirm Include and nothing showing on the Discovery page. Waited 5 mins to verify it didn't discover it invisibly.
I think I've confirmed your scenario. The distance between the Hubitat and the Ecolink was roughly the length of my arm.
Now it was time for some diagnostic testing.
I have a Z-Stick on another computer, on the same network running OpenRemote and thus (potentially) able to pair this onto the "production" network.
Removed the Cover, battery, wait 5 seconds, whip out my phone and go to the Include/Exclude buttons I have on my custom interface and clicked Include. Ecolink dance.. nothing. Ooooh. As if it didn't exclude under Hubitat.
Removed the Cover, battery, wait 5 seconds, whip out my phone and go to the Include/Exclude buttons I have on my custom interface and clicked Exclude. Ecolink dance.. Bingo!! The LED on the Ecolink flickered then started blinking slowly, even before I could get the cover on. [OpenRemote logs shows a success as well.]
Back to Hubitat and Include (Discover)... Ecolink dance.. instantly found.
Generic Z-Wave Motion Sensor 60 <-- new
Manufacturer:014AProduct Name:Generic Z-Wave Motion SensorModel Number:Unknown Part NumberdeviceTypeId:53
It's not a motion sensor, but very much better than no discover at all
Create Time 2018-05-13 13:49:34 PDT
Last Update Time 2018-05-13 13:51:08 PDT
Last Activity At 2018-05-13 13:49:39 PDT
Data
deviceType: 1
inClusters: 0x30,0x71,0x72,0x86,0x85,0x84,0x80,0x70
outClusters: 0x20
deviceId: 2
MSR: 014A-0001-0002
manufacturer: 330
I picked the Generic Zwave Contact Sensor driver and yes, it worked properly:
Current States
battery : 99
null : null
contact : closed