@jpmeijers, it seems the device is sammy-ttn.
I figured maybe looking at different dates for that device from the all-time map may reveal something.
Wild guesses ahead!
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All-time: TTN Coverage
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After messing up: TTN Coverage
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Before messing up: TTN Coverage
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Zooming in…
So, given this gateway, maybe @StreetDirt?
Yeah… 
Interested in all things QRP, LoRa, Arduino, high altitude balloons, trackers, building electronic stuff and programming things.
I’m sure @jpmeijers can fix this. 