new build lost USB connection

I recently took over a custom reprap build at my local hackerspace. The space calls it the Krakenbot but it doesn't seem to be any way related to the kraken hot head I found via searches. Anyways, the unit was mechanically assembled and mostly wired up when I found it neglected, the wiring a rat's nest of wiring. Looks like they built it with an assembled RAMPS 1.4 that shipped preconfigured with Sprinter.

Recently I cleaned up the wiring and got it communicating with Pronterface on my PC running Ubuntu. Yesterday, I got it to connect to pronterface and all three axis to home and all that.  I heated up the extruder and extruded several mm as a trial run.   But then I accidentally hit the disconnect button on pronterface with the extruder still on set to 185 deg C. After that, the printer wouldn't connect to my PC. Pronterface wouldn't recognize the board.
I was unable to reset the RAMPS board because I discovered that the S1 reset button is missing...
Has anyone ever experienced having an issue with losing communication if disconnect with the extruder heater on? Or would this be expected?

What about having to reset the Arduino board separate from the RAMPS?
The Arduino is being powered thru the RAMPS.

I will be going back next weekend to try again
I appreciate any troubleshooting guidance. This is my first build.

I just read something about a "shielded" USB cable clearing up some communication problems. And solder in the S1 or short it out with a jumper...wish I could help more

Update:
I was already using a shielded cable but was having the same issue.
Then I plugged in a USB thumb drive to see if my computer would recognize that and that seemed to trigger Pronterface to recognize the printer because the port popped right up and issue resolved.

I use ubuntu on my host, and the printer normally comes up as /dev/ttyACM0. If I reset the printer, the port changes to /dev/ttyACM1. All I have to do is hit the "port" button in pronterface to cause it to refresh its list of ports, and I can see that ACM0 is no longer there, replaced with ACM1.

If I reset again, or reboot the PC, it switched back to ACM0.

Maybe this is what happened to you??? I assume windows does something similar with its port names.

I've found that the USB-RS232 chip on the Arduino is highly suceptable to EMI. If an electrical load is switched on close by (regardless of what outlet it's plugged in to), you'll lose the connection. It really sucks when you're in the middle of a print and someone switches the window AC on and the print just stops. It stops printing, mind you, but the firmware is still running since the heaters still run under PID control. Not good since they'll stay on until you manually shut them off. I've ordered an SDRamps, and I'll print from an SD card from now on. I may even modify my firmware to shutdown if there are no commands within a certain period of time. In any case, I don't trust my machine to run unattended which greatly reduces the objects I can print.

With all the issues of ramps being interrupted by RF, I'm wondering if anybody has tried any methods of shielding the ramps boards themselves...I'm thinking Faraday cage.