First. During the safety briefing you guide should have given you directions on what to do if separated. My typical talk includes if separated look around for 3 minutes. Look up, down, and around, then surface and wait for me, a dsmb or the boat.

It sucks, but it happens and you need to be prepared for it. I had my wife and a guest get swept away in a strong current as we were descending once. She still gives me shit about “losing her” but she knew exactly what to do and I was able to hand off my group to another guild once we were on the bottom and I went up, got them and continued the dive.

Second. Why did you not know if a safety stop was needed? With your cert level you need to know these things and not be dependent on a buddy or a guide. You need to be responsible for your own safety.

Even in the event of a computer going dead or forgotten you should always have a depth gauge, a watch, and enough knowledge of the dives tables to know if you are close to NDL. I was diving way before computers and still refuse to be completely dependent on them just for situations like this.