Ramifications of Using an Incorrect Mortar Mix
Thank you for the comments. We are not sure exactly what was used because at the time we thought they knew what they were doing and, as a result, we did not pay a lot of attention. When the patio dried, however, all of the bricks were discolored. So, we started doing our own research.
Turns out that they installed the bricks like tile, with grout placed into the gaps and wiped with a damp sponge. The discoloration is from the mortar being smeared around and absorbed by the porous bricks. The proper technique is to butter two sides, place the brick, and wipe away access with a trowel. The tile technique is also likely to leave voids within the mortar that will initiate cracks due to freeze/thaw cycles.
Anyway, to make the long story short, once we figured out that they used a totally incorrect technique, it became obvious that they did not know what they were doing. Therefore, we started questioning other things. I remember seeing bags that said "Portland Cement" and I don't recall seeing them mixing in any sand. However, it is certainly possible that the bags were indeed a proper pre-bagged mix.
The contractor is on vacation for two weeks. We will ask him when he gets back. However, before we did that, we wanted to understand the possible consequences. Your comments are very helpful -- thank you.