Sky: You are right, it could have been a buy.
But most likely it was a sell. Using your reasoning, with 40% of the share volume going through on that trade, if someone wanted 100.0K would the stock price finished on the low of the day?
I ask you what is the more likely scenario? I mean Tinroad said "I have bought on the bid", but he is bringing it up as a irregular possibility, not the most likely scenario.
So it could have very well have been a buy.
Time will tell...Maybe Monday will tell.