Sounds like a common thief to me.
Cops are seldom honest enough to be common thieves. If a cop was behind this, he'd have cleaned you out at the first chance and come back to bust you the next day.... its been more than a day, so chances are damn good its a seventeen year old kid interested in nine millimeter pistols and such.
No cop would make a second entrance unless he had a warrant the second time.
Any dope missing? If there is dope missing, you know its not a cop. If there was dope missing and it was a cop, they would already have busted you.
Cops steal dope by making busts and turning in less than all they confiscated. Goes for money too. Who is going to call them on it? You are not going to say there was more dope than what they say, and if you said there was more money, no one would believe you anyway. Same thing is true of guns. They'd come in seize twenty, list ten, and let you argue they took all twenty... who will a jury believe? Who would a DA believe?
Nah. Its not LE. Its a common thief.
This isn't LE. If it were LE, you would already have known for sure.
If the guy walking the dog said on the cell phone "He's coming your way," you have a very plausible ground for thinking you are under surveillance. Need I advise the best thing to do while under surveillance is nothing?
I'd want to clean house, yes, and get rid of anything you have that might be illegal... I don't know where you are, but where I am that military grade CS is likely good enough for the night in jail, even if you have a legit reason for having it around. Cessation of any illegal activities for a reasonable time is in order. Local cops, usually ninety days is good. Federal cops, six months may not be long enough, as they are patient. Drugs and guns do not mix well with LE, by the way.