Sheila and Terry Messenger had just returned to their home in Smethwick from a caravan holiday in Great Yarmouth when they realised pet dog Oscar was missing.
Wet weather had ended their holiday early and the couple were unloading the car at their home on Unketts Road on May 19 when Oscar disappeared.
Sheila explained: "We'd gone on holiday, but come back because the weather was so bad, so Terry was unloading the car and Oscar follows him into the house.
"Terry then went back to the car, but must not have realised the dog was behind him, so when we were finished unpacking, we suddenly realised Oscar wasn't there.
"Terry's gone up along the street to try and find him and I'm panicking and getting upset about whether we've lost him."
The couple were sitting at home working out what to do next when, about five minutes after Oscar had gone missing, they received a phone call from a young man.
She said: "I took the call and he asked me if I'd lost a dog, so I've said yes and asked him where he is, and he's telling me he's in Bearwood.
"At this point, I'm wondering if it's a kidnapping and he's going to make me pay money to get Oscar back as he'd never walk all the way up the road to Bearwood.
"It was then that the boy told me how he'd got on the number 12 bus and walked up to everyone to give them a kiss, then he'd jumped up on his lap.
"This lad has seen Oscar's collar, which has our number on it, and got off the bus to call us and arrange for us to pick him up."
The boy explained that Oscar had walked up to the bus stop at William Road and followed those waiting for the bus on-board.
If Oscar had continued his journey east he might have ended up at the end of the line in Birmingham.
Sheila said there were tears of relief after the phone call and, 45 minutes later, they were reunited with their two-and-a-half year old dog after Terry met the boy at the Redeemed Christian Church of God House of Praise in Bearwood.
The 71-year-old spoke of the relief she and her 70-year-old husband felt and wanted to offer her thanks to the boy, whose name she wasn't able to get.
She said: "I am so relieved to have him back and even more so as he wouldn't normally wear that collar and we'd only put it on him for the holiday, so that's never coming off again!
"I never got the name of the lad who found Oscar, but I just want to thank him for everything he did, breaking his journey and looking after Oscar and being a good Samaritan.
"A lot of my friends are laughing about this and calling Oscar a fare dodger for getting on the bus, although I like to point out he's only two and therefore doesn't have to pay a fare.
"He's our little boy and if he'd be gone overnight, I know we wouldn't have slept a wink because of worrying, so I'm just thankful for having him home."