Disappearing Marks/Bills (and a couple of other issues)

So I have rank 6 and 7 marks up right now, and I went to complete the Diabolos mark, only to find that I need the Site 3 Key. I went to the residence in Bhujerba to get it, but the woman there said that her kids, who had the key, were gone. I read up to figure out how to find the kids and saw that you need to complete the Antlion hunt. I never did the Antlion hunt, yet the bill isn't listed anywhere on the notice board. What the heck? Did I miss my chance or something? I thought bills stayed up until you hunted the marks.

Also, does anyone know what the "Entangled Driftwood" (in Giza Plains during the rain) and the "Moogles Eight" (in Old Archades) are all about? I assume the Moogles are just there for amusement, but it seems the driftwood would have a purpose-- I couldn't find one for either, though.

In the Giza Plains, during the rain, if you push down all 6 pieces of driftwood, it'll create a path to the Gil Snapper. Also, I think Antlion is given to you by Montblanc, but I could be wrong.

In the Giza Plains during the rainy season there are rotten trees spread around the nearby vicinity that you have to cut down. They float down river to where the driftwood is to help form a bridge across. You'll know you've got all the trees chopped down when you hear a little chime sound. Then you can cross over to where the Gil Snapper is. Just to let you know however, it needs to be pouring rain or the mark won't appear. Just keep zoning in and out of that area until it does and the Seeq will come up to you and tell you when it appears.

And yes the Antlion Hunt is assigned to you by Montblanc. Just go to the Hunter's Guild and talk to him and you'll see the hunt appear on the selection board.

You need to join Montblanc's guild if you haven't yet.

Ah, I haven't been revisiting Clan Centario at all. *slaps forehead* Thanks, guys!