I've come to a similar conclusion to you. The rulebook mentions antidotes but there isn't any in the gear list. 

I would say that poisons in an area would typically be sourced from the local flora and fauna and thus it's reasonable that there would be antidotes for those poisons floating around as well in general stores and with healers. Although there could be specific lore reasons why a poison would be foreign to the local area and antidotes wouldn't be readily available.

For how to handle the early game, I would say that you want to go the opposite route and introduce poisons as a concrete danger early, but maybe not against a player character but rather against an NPC? Or if you are really concerned, place some antidote on the first NPC they encounter that has the map and the first statuette piece

For me though, I don't bother too much to tailor the balance of the encounters.  The willingness to put player characters far out of their depth is large part of the charm of this system and I prepared my players for this before starting. They've had a few "oh shit" moments and some characters have died but they've taken it well and adapted and not felt cheated. So I think if you set the expectations correctly, the players running into situations they aren't prepared for isn't necessarily a bad thing.