Nested Index Collect to gather data from multiple sheets

Hi all,

I am trying to create a sheet that pulls data from multiple others. I want to populate the person from Sheet 1 when the collection sheet column for client matches the Sheet 1 column for client.

The basic formula from one sheet works:

=IFERROR(INDEX(COLLECT({Sheet1 Person}, {Sheet1 Client}, Client@row), 1,), "Missing Person")

I've tried:

Option 1:

=IFERROR(INDEX(COLLECT({Sheet1 Person}, {Sheet1 Client}, Client@row), 1,), (COLLECT({Sheet2 Person}, {Sheet2 Client}, Client@row), 1,),"Missing Person")

Option 2:

=IFERROR(INDEX(COLLECT({Sheet1 Person}, {Sheet1 Client}, Client@row), 1,), OR(COLLECT({Sheet2 Person}, {Sheet2 Client}, Client@row), 1)),"Missing Person")

I've tried other variants with various additions/subtractions of paranthesis and the INDEX.

How should it look when nesting additional sheets?