I already did that, it's there, I didn't imagine it. I suppose it could've been a quoting error but based on the evidence, I still do not see how.
I think in HFT world, reacting that quickly is common. SMART routed it to one venue, HFT picked it up and moved their bid on the slower one. What's impossible about it?
Because IB would have routed it to the exchange where the bid was located first. I've had similar experiences because there was a quote that was erroneous and persistent (never went away unless you tried to hit it, and when you lifted your order the quote would come back).