I see a sunflower on the wall, near my uncle's claim; what does that mean?

Hint 1 of 8:

Did you watch the video about you and your uncle that was in your inventory
at the start of the game?

Hint 2 of 8:

Apparently, sunflowers had special meaning to the two of you.

Hint 3 of 8:

If Jacob had left anything particularly for you, he may have used the
sunflower mark as a "signal" to you.

Hint 4 of 8:

However, it's very dark in this particular area of the tunnel, and hard to
see anything.