I added the string ‘chem132’ to this topic to further test this. I just confirmed that neither ‘A132A’ without the 'A’s nor ‘chemA132’ with the ‘A’ replaced with a space find this topic. Sorry about the 'A’s, but I wanted to make sure those strings stayed out of the topic so that others could test the same search strings under the same conditions.
In other words, I was right and the only reason 123 found this topic was because 123 was in it by itself. 123 would not have found chem123.
Thanks for your investigation, @sam!