Refer to https://support.smartbear.com/testcomplete/docs/reference/program-objects/ocrtextdocument/checktext.html or the example that JDR2500 has provided - the same can be done in Keyword Test.
If I understand right you would like an OCR checkpoint to return a warning rather than an error. If that's the case, I you should be able to accomplish it in a script using an aqString method. For instance, once you have the OCR text object you can use aqString.StrMatches to verify a string, or substring, is included in the recognized text. Below is an example using VBScript. I haven't tested it to verify I have everything right.
Set recognizedText = OCR.Recognize(<your object here>)
StringToFind = "This is my string"
If (aqString.StrMatches(StringToFind, recognizedText) = True) Then
Call Log.Checkpoint("Pass: The string was found.")
Else
Call Log.Warning("Fail: The string was not found")
End IfStrMatches accepts an expression for the string you want to find. Working with expressions is not a strength area for me. Checkout the docs here:
aqString.StrMatches Method | TestComplete Documentation