Did not pick up from the original post that they filed as a large plan last year. I understand the instructions to key off of the number of participants as of the beginning of the plan year. They filed a full 5500 last year (presumably with an auditor's report) for 2014. Is it safe to assume that, notwithstanding the fact that they had only 98 participants at the end of 2014, they had over 100 at the beginning?
As for inheriting the plan from someone who told the sponsor they would not need an audit for 2015, I am reminded of a presumably apocryphal story from the old Soviet Union: When Krushchev became premier after the death of Stalin, an official gave him two sealed letters from Stalin with the instruction that when the first crisis occurred, he was to open the first letter, and upon the second crisis, he was to open the second letter.
After a period of time, a crisis occurred, and he opened the first letter from Stalin. It said only "Blame me". So he blamed Stalin and the crisis passed. Later, when the second crisis occurred, he opened the second letter, which said, in full, "Write two letters."