Same thing happened to me with the sweetest little back lab. I had driven about 250 miles to pick up my own new dog, June, when I saw this sweet little black lab in the middle of a busy road. She was RIGHT in the road. Unbearable to drive by. I pulled over to get her and she came right to me. Like you, I was filled with relief.
I continued on my voyage to get June now with a second dog on board. The woman who gave June to me wa surprised that I'd brought a doggie friend along for the pickup. I explained she was a very recently acquired friend. I walked the recently acquired friend to where June was and the recently acquired friend was absolutely terrified of June (BTW, June is the gentlest most submissive dog imaginable, but who knows the mind of a dog). Anyway there was no way I was getting those two precious dogs in the car together so I told the woman who was giving June to me that I'd try to find the owner of the stray and be back tomorrow for June.
The hitch was that since I driven 250 miles to get June, I was staying overnight in an AirBNB that DIDN'T allow pets. I called the AirBNB host and begged him to let me keep the lab overnight despite the no pets rule. He resisted and I pleaded and finally he relented saying his own dog was a stray so he had a bit of a soft spot for them. Thank God. I swore up and down that I'd clean the AirBNB meticulously, which I did. The bummer was he gave me a bad write up on AirBNB saying there was dog hair all over. Hah I re,moved every hair in sight and even washed the sheets. Oh well...That was the least of my concerns given the two dogs were unlikely to coexist in the back seat of my Prius.
My night with the stray dog was memorable. She was one of the dearest and best behaved dogs I've ever met and had eyes that could melt a million hearts. She followed me everywhere and cuddled up with me in bed. I was determined to somehow come home with both dogs if I didn't find the owner. Luckily, I found the owner in the morning. It was so hard to say good bye and let her go, but I did and then returned to pick up June and drive the 250 miles back home.
Because of the time spent finding the owner, June and I didn't get back to well after dark. I brought her to my farm where she was to be my new livestock guardian dog. Despite having previously lived with a goat, June was terrified of my goats. I sat with June until about 2am while she cowered behind me. I wanted to bring June to my house and get her away from the scary monster goats, but she was NOT getting in the car again so I made her her own little house where she could hide. She hid in there for a few days. Over the next few days, each time I checked on her, I'd only see her little pointy ears poking out. Finally she emerged and over time everything worked out. Now she spends her days running through the fields, completely at ease with the goats. Not a Christmas story, but still a happy ending. I still think fondly of the little black lab. I told the owners that if they ever ever needed to re home her to come straight to me.