D1 Mini; is there a fuse? While this board (listed on ebay as D1 Mini NodeMcu Lua WIFI ESP-12F ESP8266 WeMos 4M Bytes Development Board Kit) was powered by usb, I accidentially shorted between the gnd (G) and 5v pins on the left, and some magical smoke escaped.

I can no longer power the device from usb, but it works nicely if I supply it with the right voltage on either the 5V on the left or the 3V3 on the right.

So something has burned between the 5V on the usb and the 5V on the regulator.
I have tried measuring the components with an ohmmeter, and compared it to a working board, but I can measure no difference.

Is one of these tiny components a fuse, or a diode to prevent backwards voltage from board to pc, if the board is powered on the pins?

Or could the short between 5V and GND have caused a track to burn?
Try measuring with a voltmeter to compare the good board to the bad one. If it is the diode as mentioned in the comments under the question, you should get a different reading on the bad board. It should be fairly easy to replace if you have a soldering iron and a steady hand.