Being a victim of theft always is never good news.
So was this reported? Call the police and file a report? Was there cameras within the area to see who the person(s) are? As stated, no car alarm? Do you have car audio stickers on your vehicle because that will draw attention. I've actually had a car follow me home, but I drove past it pretending I didn't live there and kept driving.
Hate to say it but most thefts are within friend groups. Or know someone within that friend with another friend to go smash and grab. Start looking at pawn shops and craigslist.
Next install you do I wanna make a strong advise and that's spend the extra $$ on good hardware. It sounds like your install wasn't secured enough. I.e., using draywall screws on everything is just way to easy. My sub box was bolted down to the vehicle and the subs themselves I used spiked t-nuts and 1/4" allenhead bolts. Would make it literally impossible to just remove it. Same with my amps....bolted down. This way, if they even tried, they couldn't. My goal was to make it difficult for them.
Best of luck ta ya.
'97 4 dr. Tahoe
Polk Audio MM6501
Wolfram amps 3000.1, 125.4 coming soon
2 Sundown Audio X 15's Tuned @ 30Hz.
Interstate battery/Royal Excelene/KnuKoncepts Kolossus wiring