IS there power to the alarm panel (and remote keypad if it has one!) , because you had a power cut , when the power came back on it may have surged the panel and taken out either the external spur fuse , or even the internal fuses on the alarm pcb, or it could have even spiked the memory on the panel, or even blown the dc circuit on the panel , but that would be rare as they do normally have some protection.
This could have happened because your house wiring may be quite old and you may not have trip switches & an rcd, which means that due to slower disconnection times (and if the alarm is wired on the lighting circuit then it could be as much as 5 seconds) as you do not have to comply with the mandatory 0.4secs for sockets , then it could be that the surge did some damage.
Check power etc and let us know how you get on.