Yes, Olof and Tobias would definitely be used in a Scandinavian name, most likely Norway or Sweden and if he listed Stockholm on his Instagram, then that's the capital of Sweden.
Hallin sounds a Swedish surname too. Hard to say if his parents emigrated to the US and he was born here and he has a US passport - or if he has a Swedish one and was just living in the US.
Either way, if he left the country on a flight, the police would know.
The fact he was involved in Bitcoin and that kind of cryptocurrency trading makes me nervous. He isn't the first person in that would to go missing.
MOO.