The State has near-limitless resources, therefore they MUST be held to the highest of standards.
I'd even be in favor of censuring/firing the investigator involved who left information out of the warrant. Future defense attorneys will be able to bring this up on every affidavit or testimony he gives and some portion of cases will fall apart as a result of this.
Local prosecutors and police do not have limitless resources… poorly used and a lot maybe, but I think people would be surprised what the constraints are.
Technically true but just a lawyer's time (for "free") is significant. Throw in other prosecutors, investigators, etc and it begins to look "limitless". And beyond that, with a gun charge, it could be escalated to the state level pretty quickly. Alternatively, if he illegally possessed it - common if there are drugs - it could qualify for Federal charges.
It's up to the prosecutor(s) to decide what the charges are and at what level, therefore they get to decide what resources to expend.