Help me analyze this INDEX/MATCH function

I am trying to figure out the spreadsheet of a coworker who has retired, but left no training or documentation behind.
This is one part of a larger formula, and it's giving me so much trouble!

Let's say this formula is in Sheet1. I've simplified the references to make it easier to read.
=(INDEX(Sheet2!A:AP,MATCH(C1,Sheet2!A:A,0)))

As I understand it, since the range for INDEX is more than one column, the creator of the formula should have used a column reference as a 3rd argument, but there isn't one.
I am getting all zeros back from this formula, no matter what row it's looking at. I think there is an error here.

What column data will this return by default since the creator did not specify a column for the INDEX?

Any help is appreciated. I"m pulling my hair out with this one.

I cannot replicate your observation. When I do something similar (multi column reference) and only give it one coordinate, Excel gives me a #REF error.

Thank you Mr. Shorty. Because of your observation, I realized I messed up. The first arguemnt of the INDEX function (which has been simplified for the purposes of this question) was a named range that was named VERY similarly (1 letter difference! ) to another range. The range in question is indeed a single column range. So I have solved my problem. Can't believe how long I spent on this! Sometimes you just need other eyes on something. Appreciated.