You should water new seeds twice a day. The ground that they are on/in should never get dry. It is almost as much work as taking care of a newborn baby......well, not as much, but you get the point.

What type of grass was there originally? Whatever that is, you need to plant the same type or else you will have one of those funny looking lawns that change colors. You would think that grass is grass, but it isn't. Just drive around an look at people's yards, and you will see what I mean.

Regarding the hay, stuff like that is helpful but not necessary. There are many different things you can do that have the same effect. It really only has an effect if the seeds were in danger of either washing or blowing away...or perhaps being eaten by birds.

Lastly, "about 4 weeks ago" was July 1. That would just about be the worst time of the year to seed. Keeping it moist is very difficult at that time, and the summer heat requires you to baby even the baby seedlings.

So, in sum, here is why I think our lawn didn't take:
1) not enough water
2) didn't plant at the right time of year

If I were you, I would relax a couple weeks, perhaps pick some weeds if they annoy you, and then overseed on September 1. If you really want to make sure the seed takes, do the following:
- rent a slit seeder so you can make sure there is seed to soil contact
- topdress with compost

Even if you don't rent the slit seeder (which most people don't want to do, topdressing with something would be very helpful.

If the contractor is responsible for seeding, I do not think anyone would consider what he did as adequate. Seeding in middle of summer with straw/mulch? Unacceptable if you ask me. I would get on their case about that.

Well... I meant seeding WITHOUT straw/mulch is unacceptable for a contractor right now.

The seeds are not staying moist. Figure on watering several times per day in a full sun location. Seeding in summer probably isn't going to give you the best results due to the conditions.

To be more specific, when I say watering several times a day, I mean very brief sprinkles to keep the seed and surrounding soil moist.

To sum up, you need to keep the soil moist to get grass seed to grow. In the shade, the soil dries out much less quickly, so the process is more forgiving. In full sun, you have 2 basic ways to help keep the soil moist. The first is sprinkling the area several times a day. In your case, that should be fairly easy because you could just hand water the strip. The second trick is providing some sort of artificial shade for the seeds to help conserve water. Straw will do this as would a thin layer of compost.

As to where to go from here, I would yank up all the weeds, sprinkle some more seed, cover with straw and commit to watering twice a day until the seed is up.

Inconsistent watering when the seed is germinating can let it dry out and die.

Also, cool season grasses just do not want to germinate when the temp gets hot. The way mother nature designed them. Those in the sun could well have gotten hotter and therefore not been as inclined to sprout in the higher temps.

Either way, put out some more seed when it starts cooling a bit in your area and follow the advice above on keeping it moist but not saturated 24/7 until it has been up a couple of weeks. Usually about six weeks. The first 3 to 4 weeks, as you may have demonstrated, can be critical.