It is not an "ingredient", so it would never be listed there. The pH level changes slightly from batch to batch (and most people don't know or care much about the pH that it is used very often as a marketing tool) so you generally won't find it on the bottle.

I would worry less about the exact pH and more about whether the product is formulated specifically for processed hair. Shampoos for color treated hair would be a viable substitute in a pinch.

So don't worry too much about specifics. Concentrate on overall results. Even the fact that a shampoo is "sulfate free" doesn't guarantee that it will work well for processed hair. I've had some that absolutely tore the hair up. The specific ingredients or the pH is less important than the sum of its parts.

In other words, you can't judge a shampoo based upon it's specific ingredients (or lack thereof) or the pH level, or how sudsy it is, or how it smells, etc. The really important thing is how it maintains the condition of the hair after 6-8 weeks and beyond.