Firstshop's vanishing stock

I ordered an "inverter-trolley" (actually a power-trolley) from Firstshop last week; this was shown on their website as being "in stock" and I was informed by their support team via online chat that they had 150 in stock so I placed the order. I received an email on 6th October that the order was being prepared for shipping. I received an email today (12th October) informing me that the unit was out of stock and I would have to wait until early November to receive my unit. I conclude that "my" unit was sold to somebody or some organization that has more influence on Firstshop than do I. I had dealings with First Technology (I believe Firstshop's parent company) many years ago and didn't like them then - in a way it's good to see one's original judgement confirmed.