San Francisco, California – For a full two days, the little dog Roo was missing before he was finally found in a train tunnel. At first, the train drivers even assumed the four‑legged friend had been run over – until he suddenly moved!

Roo had just been adopted and microchipped. At his new owners' home in San Francisco, the dog got scared and ran away.

As People reported, his caretaker searched frantically everywhere for him but couldn't locate him at first.

No wonder: The cute four‑legged friend had ended up in a train tunnel, where he hid for two days!

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In fact, train engineers discovered him a day after he disappeared. Because Roo was completely motionless, they assumed he was dead.

It wasn't until the next day that another rail employee noticed the dog was still moving!

The team from San Francisco Animal Care and Control was quickly called in to rescue the pup.

In a video shared on Instagram, the rescue team can be seen pulling the dog out of the dark tunnel where he had hidden.

Although Roo was unharmed, he was completely terrified. Once the responders managed to put a leash on him, his fear quickly turned into joy.

"He was terrified at first then was thrilled to be rescued," the post read.

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A scan revealed that the dog had a microchip, allowing the shelter to quickly identify his owners.

"He was recently adopted & got spooked & ran. His person was looking everywhere for him & was thrilled to be reunited with him," the post continued.

For Roo, the adventure ended happily. He can now fully enjoy his new life with his owners – hopefully without any more escapes!