Let the secret number be \( x \).
According to the problem, we can set up the equation as follows:
\[ x - 1567 + 2679 = 4780 \]
First, we simplify the equation:
\[ x + (2679 - 1567) = 4780 \]
Calculating \( 2679 - 1567 \):
\[ 2679 - 1567 = 1112 \]
Now, substitute this back into the equation:
\[ x + 1112 = 4780 \]
Next, we isolate \( x \) by subtracting 1112 from both sides:
\[ x = 4780 - 1112 \]
Calculating \( 4780 - 1112 \):
\[ 4780 - 1112 = 3668 \]
Therefore, the secret number is
\[ \boxed{3668} \]