I am unable to find anything in the rulebook that explains if mundane ammunition is recoverable, damaged, or destroyed after being fired. Are there any official rules on this?
Errata (30 October 2019) has now clarified that ammunition is destroyed on use.
CRB page 559 details consumable items:
An item with this trait can only be used once. Unless otherwise stated, it is destroyed after activation. ... Consumables include the following subcategories, ...
The heading 'Ammunition' follows this rule.
The slightly odd thing, however, is that at least on Archives of Nethys, the direct entry for the ammunition I checked does not mention the trait consumable (e.g. bolts and arrows). And the section on ammunition on page 559 talks specifically about magical ammunition, if under the non-magic-specific heading of 'Ammunition'.
Further down on CRB page 559 (under the heading Ammunition), the rules state;
Regardless of whether an attack with magic ammunition hits or misses, launching the ammunition consumes its magic.
Taken on its own, this would suggest that mundane ammunition is not consumed on use.
This rule would be unnecessary if the physical part of the ammunition was going to be destroyed (as it would have been in PF1).
If we were not meant to count ammunition at all, then Paizo could have sold unspecified quantities of arrows (e.g. selling a quiver of arrows, rather than bundles of 10). So there is a sense in which they are always consumable (i.e. immediately after being launched they cease being as readily available to use).
So far as I can see, there are three possible interpretations:
1) The second quote above is an oversight, there is a typo omitting the consumable trait from mundane ammunition, and all ammunition should be consumed on use (as would happen in PF1).
2) Magic ammunition's magic is consumed on use, but the physical part of magical ammunition survives. But there is a typo omitting the consumable trait from mundane ammunition, and purely mundane ammunition does not survive use. In my opinion this the weirdest stance to take.
3) Mundane ammunition, and any physical or mundane part of magical ammunition is not destroyed on use. But ammunition that has magic always loses all of that magic on use.
My reading of the RAW:
I would suggest that number 3 is the most RAW way of reading the rules. Though I do not think it is perfectly clear that this is what they intended.
What I plan on using:
After considering this for a while, what I plan on using as a GM is a modification of 3. I would rule that mundane ammunition is broken by default after use, and that there is a 10 minute activity to recover and repair them (which would have similar requirements to repairing shields). This has the advantage of providing more 10 minute post combat activities - to match those like shield repair, focus recovery, etc... However I would also tweak it so that circumstances may change this, and that for example, wooden ammunition launched into a fire elemental is unlikely to survive.
N.b. As an aside technically you never poison ammunition itself, but rather the weapon that launched them, so there is no RAW issue of ammunition retaining any poison.
Using Ammunition Destroys It
Per the latest (released 30 October 2019) 1.0 errata for the Core Rulebook, using ammunition of any kind destroys that ammunition. It can't be recovered. (See page 3 of the errata document)