Consider if you have potential duty responsibility upon arrival (reserve assignment window, drug test).
But I'd probably check company policy first, it's possible they have language about "ownership" of pos space tickets, ie you if it gets cashed in then they want the cash back. Although in this case I'd think the ticket is still valid and unused and they can cash it out if they want (there's an exchange process between airlines, and that's opaque to us). The voucher was for your inconvenience, it did not negate the ticket.
Probably enough of a grey area that if anyone had an issue they'd just tell you not to do it again, but there's a slight risk that if your company spun it as theft you could get in big trouble.