One little quesition, how in the world did they steal an iMac 😂
If you have your iCloud Account signed in and Find my Mac on you can locate the Mac. Just go to www.icloud.com, sign in and open Find my iPhone option there.
Or you can do that on your iPhone, just open Find my iPhone and locate your Mac.
If that didn't help get in touch with Apple and the local police for help.
I am afraid Spotify can't give you what you want but if you want you can contact to them.
To contact support, please fill out the online contact form. If, for whatever reason you would prefer not to, or you cannot use the form, support can also be reached on twitter by reaching out to @SpotifyCares, or on Facebook by sending a message to the Spotify Cares Facebook page. Please be aware that responses may take anywhere from 24-48 hours depending on the volume of tickets they are currently handling.