To be clear, I do not blame the provider (Three in my case), although I agree they could have handled it better. Your case was much worse.

I blame Sailfish for not providing any way of re-registering the SIM other than through a power cycle. My previous phone (running Palm OS) always asked for the SIM PIN every time I went offline and on again. It gave me the warm fuzzy feeling (maybe wrong, who knows) that offline really meant offline, with the GSM modem switched off.