You put a +1/+1 counter on Tomakul Scrapsmith if you don't put an artifact card into your hand with its ability, even if there wasn't an artifact card among the milled cards.
2022-10-14
If a replacement effect causes the milled cards to be exiled instead of going to the graveyard, this effect can still apply to the cards "milled this way" in exile.
When this creature enters, mill three cards. You may put an artifact card from among the cards milled this way into your hand. If you don't, put a +1/+1 counter on this creature. (To mill a card, put the top card of your library into your graveyard.)