many people gamble in many options continuously all the time. did trades like this occur in the market for Splunk every day? did this trade significantly affect the price or volume in Splunk options? If it's part of a very common pattern of random trading, then the unusual thing is the acquisition, and not the trade.
And a suspicious trade itself is not enough evidence, there needs to be evidence of an inside information conduit to make the case.
I'm not take sides on the suspiciousness of the trade, I'm pointing out what the language of the evidence should look like to raise suspicion.