So sorry about this, shannon.
I do want you to know that this WILL NOT cause a miscarriage, even with as distressed as you were during the argument, and for the length of time it happened. Miscarriages do not happen due to stress, and emotional turmoil. 90% of the time (possibly more), they happen be because of a problem with the egg or sperm, a genetic defect, a cell division issue, or chromosomal defect. If miscarriages were caused by high-stress moments, there would be no babies born in third world countries, or in wartime situations...and we know that these are VERY stressful circumstances. So, do not blame yourself.
Secondly, didn't you have a spotting/bleeding episode before? Or am I thinking of someone else? If so, it just probably decided to rear it's ugly head at the worst possible moment, and now you're attributing it to the argument and distress. I have had two different spotting episodes during this pregnancy, and I had a great ultrasound last week, with a healthy baby so far...so it does not signify the end for you, at all. Please do get a scan, and kick your feet up, and relax. It was a rare moment for you two, I assume, so just go take a shower, drink some water, and have some time alone to defuse. This type of stress is worse for your mental well-being, and for your spirit...as of right now, it did not harm your baby.