In all probability this is all bullshit. But it is NOT outside the realm of possibility. The feds are starting to use provisions of the PATRIOT act to expand their powers beyond the scope of the constitutional limitations, much like they abused used the limited powers the RICO statutes gave them to combat organized crime. It's only a matter of time before local LEOs follow suit. They have the means to get around the constitution by trying to apply PATRIOT to include drug offenses.
But unless they invoked the PATRIOT act, I don't see how they could have possibly gotten a judge to sign a warrant based upon the fact that seeds were delivered to your home. No judge in his/her right mind would sign off on that without further corroboration. They most CERTAINLY overstepped their bounds bringing a drug dog onto your property for it "to alert" to the presence of drugs/marijuana.
As for downloading your computer files from your hard drive, I'm pretty sure that didn't happen. Why the hell would they take the time to download your drive (couple hours or so for a small hard drive with much of anything on it) when they can just take the whole computer tower? Believe me they aint shy about doing that.
Cops are no different than anybody else, they do their job (as they see it). Their job is to bust you, and do so with as airtight a case as possible. No cop, prosecutor, or judge would even try to arrest you on such flimsy evidence, much less take any assets or money. A first year prosecutor would know that the entire search was based on nothing, and no matter WHAT they found, it would be "fruit of the forbidden tree", and inadmissible. Unless they invoke PATRIOT. Now if they had found all of that during the execution of a valid warrant, you'd be screwed. They would make sure that their case is a bit stronger than that. I have seen them prosecute on some flimsy evidence, but nothing like what you describe.
They can take anything illegal they find in your home whether or not it's on the warrant, as long as they are in your house legally, meaning a valid warrant for anything. Under RICO, they can even seize cash or anything saying they believe it was proceeds for illegal activity, it will be up to youto prove otherwise. If they come in with a bad warrant, you are still fucked because you'll not get much, if anything back, and even that will take hiring an attorney, and lots of money. So its win/win for law enforcement anyway it goes. They know this.
IF you are telling the whole story, and I am sure there is more to it than you're telling (IF it really happened), nothing found during that search can POSSIBLY be used. Any Judge or prosecutor would realize this and make the cops get more evidence prior to bringing any charges.
Now............................For all of you who are saying that they "can't do that", either you have never had the misfortune of running afoul of the law, or are being incredibly naive. They CAN DO ANYTHING they want to. And they do quite frequently. Whether or not it holds up is another story. But trust me, get a cop pissed off at you and he can make life a living hell. He can do anything with impunity as long as he is "acting in good faith". I have seen searches hold up in court because the officer acted in good faith in believing that a warrant existed. Yes, they can search your home without a warrant being on the premises or in hand if they believe that evidence could be destroyed or hidden prior to the arrival of the warrant. They can seize anything, and let you sort it out in court.
For all of you who believe that the constitution still gives us some measure of protection from the abuse of power, I HIGHLY suggest you read the PATRIOT act. A good synopsis can be found at the ACLU website. I can assure you that it will scare the living shit out of anyone who believes in personal liberty. They are already using the provisions PATRIOT to prosecute gangs, internet crimes, and a host of other things not originally written into it. They are rapidly expanding the scope of the act to include things that were never intended to be covered by it. The US government has already stated that the drug problem is "a matter of national security". It's not a far stretch to think that they could expand that to classify possession or distribution of illegal drugs as a threat, thus making the perpetrator an enemy combatant under PATRIOT. DO NOT for one minute think it isn't already happening.