SDK 1.12.3 Doco references function name loadFile() ~
Ref: Inside Playdate with C
But this function does not seem to exist in the SDK on Linux.
I guess it's really load() as found in pd_api/pd_api_sound.h ~
struct playdate_sound_sample
{
...
AudioSample* (load)(const char path);
I've only just started playing with it, but I'll update this if my knowledge changes.
EDIT: Also newSamplePlayer() does not exist either, it's newPlayer().