Docs: Add a "Missable Locations" Question to apworld FAQ (#4965)

* Docs: add a "missable locations" question to apworld_dev_faq.md

Basically turning the conversation at https://discord.com/channels/731205301247803413/1214608557077700720/1368996789260128388 into a FAQ entry.

* feedback

* qwint feedback

* Update docs/apworld_dev_faq.md

Co-authored-by: Scipio Wright <scipiowright@gmail.com>

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Co-authored-by: Scipio Wright <scipiowright@gmail.com>

docs/apworld_dev_faq.md

@@ -122,3 +122,21 @@ Concrete examples of soft logic include:
 - Buying expensive shop items might logically require access to a place where you can quickly farm money, or logically require access to enough parts of the game that checking other locations should naturally generate enough money without grinding.
 
 Remember that all items referenced by logic (however hard or soft) must be `progression`. Since you typically don't want to turn a ton of `filler` items into `progression` just for this, it's common to e.g. write money logic using only the rare "$100" item, so the dozens of "$1" and "$10" items in your world can remain `filler`.
+
+---
+
+### What if my game has "missable" or "one-time-only" locations or region connections?
+
+Archipelago logic assumes that once a region or location becomes reachable, it stays reachable forever, no matter what 
+the player does in-game. Slightly more formally: Receiving an AP item must never cause a region connection or location 
+to "go out of logic" (become unreachable when it was previously reachable), and receiving AP items is the only kind of 
+state change that AP logic acknowledges. No other actions or events can change reachability.
+
+So when the game itself does not follow this assumption, the options are:
+- Modify the game to make that location/connection repeatable
+- If there are both missable and repeatable ways to check the location/traverse the connection, then write logic for 
+  only the repeatable ways
+- Don't generate the missable location/connection at all
+  - For connections, any logical regions will still need to be reachable through other, *repeatable* connections
+  - For locations, this may require game changes to remove the vanilla item if it affects logic
+- Decide that resetting the save file is part of the game's logic, and warn players about that