Oh OP, it's clear you only came here to bitch and have those who never think a woman can be in the wrong feed your ego and make you feel victimised.
Using logic and common sense, you said the store was packed, you admitted yourself you took 5 minutes (this is a lengthy period of time if you are in a queue waiting). What you fail to mention is that your husband could not start having the shopping scanned until he had the Costco card - which you had. Therefore, your 5 minutes mattered and held up the queue as nothing could be done until he had the card as it was his turn next.
You also admit he tried to call you, clearly he tried to reach out and ask you to come back, but you did not answer. Any person at this point would shout to get your attention to ask for you to come back. He didn't swear, asked you for the Costco card and then when you responded asked you to pick up the phone. All this was said in a raised voice, I sincerely doubt he was ranting and raging or even swearing as I am sure you would have mentioned that.
It's quite apparent he raised his voice to get your attention and you are now being dramatic. I am certain that if you were in his position you would also raise your voice to get his attention.
You have been overly dramatic throughout your posts and come across quite self absorbed and as though you are so hard done by, over such a non-event.
What your husband is like on a daily basis, no one knows, in fact you could even be a nightmare in reality. Nonetheless, in this situation you have been over the top and made it in to something that it never was. Solely on this event, you are being ridiculous and your husband only shouted to get your attention.
As for the lady apologising I assume it was simply because she felt she held you up when you were needed, and as for those looking, people stare when someone coughs loudly. You are just seriously trying to make this in to something huge.
It's time to get a grip and move on, and perhaps remind those that without the Costco card your husband was stuck.