What happens when you leave stuff in an apartment when things God bad

Please give more details.

Did the apartment flood? Did it burn down? Did Ninja's attack and take over?

You really need to add more to this if you want accurate answers. Making us guess at the situation is not going to get you the right answers and will just be a waste of time.

Don't worry, the landlord will let you know about whatever mess you left for him!

You can expect it to be disposed of, after a period (depending on area) if you do not get it.

Any question on law needs to include your general locale as laws vary by area. Most areas have rules for abandonment of property. Generally the landlord has to make some effort to find you and arrange for you to pick up your belongings. But as long as they follow local laws, they can declare property abandoned and either confiscate or dispose of the property.

Local abandonment laws are generally 30, 60, or 90 days.
However, a few places in CA, for instance, have other laws that prevent landlords from disposing of possessions (some have to put in storage and pay for one month, for instance), and again, you have to check with the city or town.

Expect someone to put it in paid storage YOU will have to pay for... or have it end up at goodwill.

If it was left in a place I owned or rented that's what would happen... as soon as I could legally get rid of it.

You wouldn't however be entitled to indefinite free storage.

Someone who didn't know any of that might toss it in the dumpster a lot sooner. Then good luck getting it back or any of its value.

Best thing is to NOT leave it behind