Most likely the power surge caused a CMOS issue with the battery. This can cause the boot order to change.
Definitely a good idea to have a surge protector connected. Just be sure to invest in a good strip. Any strip is better than no strip, however, it is worth the extra investment to get a good strip or other protection.
Also, you seem to understand the 'terminology' quite better than many others, so Kudos there.
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"My greatest experience in fixing electronics has come from having kids" -CCC