Something similar happened to me just now. I had a reservation for the IB 267 flight. When I checked the booking management, it showed me a screen warning me that the flight was changed to IB 261 and inquired if I accepted or not. I did not receive any email with the change. I called IB and explained that I'd need a place to stay since the flight they wanted to assign departed at 7am of the next day, the agent said I can claim any costs related to the flight change. During the call he also emailed the new schedule and it has the new 5 digit PNR.

Here's an unrelated question: other than my hotel / meals expenses, this is a case for claiming the EC-261 compensation?