Not sad, just correct:
http://media.wizards.com/2015/downloads/dnd/BasicRules_Playerv3.4_PF.pdf
D&D Basic rules, p70:
"You can also interact with one object or feature of the environment for free, during either your move or your action. For example, you could open a door during your move as you stride toward a foe,
or you could draw your weapon as part of the same action you use to attack."
The rules clearly state that you can only draw your weapon (singular, only one weapon can be drawn this way, you need Dual Wielder to draw two) as part of the attack action, not draw, attack, and then sheathe. The line I bolded there is a specific rule. Specific trumps general. You can't use the general rule to turn around and override the specific rule on drawing as part of the attack action, to both draw, attack, AND sheathe it. Once you finish attacking, your action is over, as is the free object interaction. You don't get a second one.
What on earth makes you think a DM would allow you to interact with your weapon
twice anyway? When the actual rules text says, "you can also interact". That doesn't say "as many times as you like to, to do anything you want". Drawing and sheathing are two separate, distinct interactions, separated in time (you're attacking in between those two interactions).
Two is different than one. When you interact the first time, you are drawing the weapon. Then you "stop interacting with it freely" and attack with it, thus ending your "free interaction" for the round. You cannot then, after the attack, interact yet again, to achieve a completely different (in fact opposite) result.
If you tried to even argue that you can draw a sword, attack with it, sheathe it, and then use the same hand that already interacted with the sword twice (aside from attacking with it) to load a crossbow in the other hand before firing it, I would just love to see you mimick that frantically at the game table. It would be total comedy. That's just not going to fly every round though.
I suspect the only person who will be sad is you when you try to pull this off on a DM who will likely see it for what it clearly is, a munchkin forum exploit designed to bypass an actual explicit game rule, and shut it down.
On the very next line we see :
"The DM might require you to use an action for
any of these activities when it needs
special care or when it presents an unusual obstacle. For instance, the DM could reasonably expect you to use an action to open a stuck door or turn a crank to lower a drawbridge."
Sheathing a weapon requires special care by any reasonable person's definition. Have you ever tried sheathing a sword that quickly? I don't recommend it. This is not going to work without the DM being on board, and with the latest errata, he or she isn't likely to.
Good luck though. I would allow you to drop your sword and score an own goal though, because the first thing a smart opponent would do is pick it up off the floor and use it against you. Or maybe he'd just run off with it, seeing that you have disarmed yourself and therefore can no longer even get an AoO.