I suspect that the problem is one of four things.

1. D3 is shorted
2. D2 is shorted
3. C2 is shorted
4. The PCB has a whisker or other etch problem between VIN and GND.

My suggestion is to start by lifting one side of D3 and D2. To remove these components, you will need to get some solder wick to remove the solder from the leads. With one lead lifted in the air, check across this component is to see if it is shorted. Also check VIN to GND to see if that short ( low resistance) has gone away. After eliminating the diodes, the remove C2 and check across it for a short . Also, again check VIN to GND on the board. If the diodes and capacitor check OK, then I wonder if the PCB has a tiny whisker of tinning or copper that is shorting VIN to GND. The best way to find these is usually visual inspection under a microscope using a known good board. Given that you only have one board, use the best magnifying glass you have. Look for any connections, solder splashes or bent leads between GND which is that areas of the PCB that look like hatch or waffle pattern and VIN. Around C2, these areas get pretty close. Make sure to look at both sides of the PCB. You can also run a sharp needle point around solder pads in an attempt to break a whisker that you cannot easily see. The area of the PCB to concentrate on is that area that got hot when you powered it up.