Is there a way that I can see when a Bluetooth device was last connected to my Windows 10 laptop?
There's timestamps and device states (like install, initiate, ...). If you cannot identify the device (should be BTH something for Bluetooth), connect the same device once more and look at the tail of the log to find the device ID.
If you go in "Devices and printers" and select a paired device, you may be able to find the last connection time there.
Go in the hardware tab, click "Properties", then "Details" and choose the property called "Bluetooth last connected time".
In my case, the time appears to be shifted in the future of two hours, but the minutes are correct.