Chick Matthews is one of the debtors Strauss will mark in Chapter 2. Head to Guthrie Farm in the Heartlands, near Emerald Ranch. You’ll be in a chase so bring a bonded horse with good speed and stamina.
Once there, approach one of the strangers in the area and ask them where Matthews is. He will point you to the debtor’s direction in which the latter will promptly ride away on a horse.
As easy as it is to just shoot him, hold the thought and keep chasing after him until you close the distance. Nab him with your lasso and hogtie him.
Loot him to get a treasure map. Inspect the document and it will be marked in the map. From hereon, you can leave Matthews tied, kill him, leave him in the train tracks, or whatever you want to do with him.
Whatever you decided on, follow the marker and head to the marked spot in the map. Find the large tree in the hillside and search the hole in the middle to find the debt money. Collection complete.