acknowledgement of an appointment

Having helped my very anxious and suicidal friend to complete his PIP forms, he received a letter from ATOS (at 10am on 16 Sept) to say they were writing to some parties for more evidence and that if a consultation was required they would write to him separately. At 11:43 that same day he got a text from ATOS saying they were in the area for next 7 days and if he wanted an appointment then to call them. As this contradicted the letter, he did not ring them and awaited the possible appointment by letter. Now DWP have written to say they'd "informed him earlier" of an appointment on 11th Oct and that he failed to attend. But he had received no appointment by letter, text or phone call (or any other correspondence) from them in between. He has replied with copies of all texts and letters he received since submitting his forms but is worried that he cannot prove he did NOT receive notice of this 11th Oct date. Do they not employ a way of confirming appointment letters have been received and indicating whether a person can attend or not? Do they not have a duty to prove that he did receive it? He is now beside himself with worry

There has been no decision yet, just that they will disallow his claim unless he provides them with a good reason for not attending the appointment.

Hi. Thanks for your prior advice, which has been followed.
In relation to a different friend who had applied for PIP, can you please advise on whether you think the process by which he has been assessed is legally correct?
*After submitting his claim in early August and receiving a text to say it was being considered and he would be told if he needed a consultation, he was admitted to hospital from 30 Aug through to 2 Sept. He was discharged to his daughters home for care.
* On 22 Sept, having received no letter or phone call or text during the intervening time, he was sent a decision letter that he did not qualify based on him not going to an assessment on 3 Sept and not having a good reason for this. He had not received any notice of this assessment, nor had he been asked to provide any reason for not attending.
* After numerous attempts to call, he eventually got a connection to DWP on number given on letter on 5th Oct. He explained that he'd received no appointment and that he had been in hospital immediately prior to 3 Sept and could provide evidence of that. He was told by the telephone operator that she just took calls but would pass the message onto her supervisor. He had rung purely to explain that he had not received the appointment, not to request a Mandatory Reconsideration. The notion that his call was being taken as a request for Mandatory Reconsideration was not explained.
* On 10th Oct, he received a letter saying that he'd requested for his claim to be looked at again (he did not realise this was what he had done) and that they had been unable to change the original decision. He was directed to the Appeal process.
* My friend is very confused, as the decision does not appear to have been made on any of the statements and evidence of his claim but simply on him not attending an Assessment which he knew nothing about.
Do you think he should be seeking further advice on the legalities of this as it seems to have been dealt with very unfairly?