How to identify which schema calls a function in another database without schema?
You can get the current schema by using the System Information Functions


current_schema[()] returns text: name of current schema
current_schemas(boolean) returns text[]: names of schemas in search path, optionally including implicit schemas


I don't think dblink passes the context of the functions executed from the original database. So you'll have to wrap those functions and explicitly pass the context, perhaps by making the function variadic

CREATE OR REPLACE FUNCTION public.guardarTransaccion("tipo" text, "idRemito" int4, "idPicking" int4,
  context DEFAULT '{}'::text[] )


Then call it like the context explicitly. I would probably just think of a better way to engineer the system.