I agree that she SHOULD have called you back in 24 hours, at max, by the end of the day on Friday.
I have a 2 1/2 year old (will be 3 in March) who also has speech for childhood apraxia of speech. His speech is through EI right now, but once he turns three, it is handled by the school district....it is no longer EI. The school district has different policies about how things are handled and it is much more structured and goal oriented (I know this cause I have an older son with ADHD/possible Aspergers).
An hour is a really long time for a child to sit, especially a boy, and if he has sensory issues as well (which it sounds like he might) they need to incorporate some movement or at the least some motor breaks. You might also help by giving him some motor/heavy physical work/activity right before you take him if you can. Does he get OT too? Sounds like maybe he could benefit from that too, and I would recommend you request him to be evaluated for that. It is likely that if he requires OT and ST that you could get him in the early childhood preschool that the district should be providing.
IMHO, I would have called and just left a message and said to please call or email you. I would not have left recommendations on her voice mail because she may be feeling defensive there since she is the therapist. Not that I don't think you have a valid point, cause you do...you are his Mom, you know what works best for him. But I would wait until I actually got to speak with her before giving recommendations. AND if she doesn't respond to you or won't communicate with you adequately then yes, you do need to call an IEP like a previous poster below suggested. I am always one who tries to work directly with those working with my kids....some teachers/therapists don't have to have those formal things down in writing to work appropriately with your child, maybe they just needed to take a slightly different approach and once you bring that to their attention, they do it, and it's fine. But others do need to have it down in writing, and it is to your benefit legally to do it that way.
I do think it very unprofessional and inappropriate for her to be saying those things about your son to others. It is REALLY hard for our kids to sit and work so intensively on things that are hard for them. Talking about a particular child to other parents is wrong. If there were difficulties and their children were in the room, she could have said, we had a rough day or something and left it at that.
That time frame is very ambitious for a 3 year old.....I would maybe ask if he could have two 1/2 hour sessions a week instead of 1, 1 hour session. I know I struggle with EI with this as well, trying to get an 2 1/2 year old to do a 1 hour speech session is just not realistic....but it the way their system "works"....in one hour time slots. And if they won't, then again, call an IEP, and be prepared to present to them why this is needed (with some research to back it up). Try to take a collaborative approach with them. Say, OK, this isn't working. What can we do to make it work? If therapy isn't working it's not the child's fault, it's the therapy that needs to be changed. Not all kids work the same/have the same issues so if something's not working for a particular kid, they need to be flexible to change things so it WILL work. Have some ideas in your head and have research done to back up why you think it will work/be helpful so that when they question you they will learn that you have done your research. The more they see that you know what you are talking about, the less they will try to steamroll you. The wrightslaw website that was mentioned below is a good one.