The pearl of power (Dungeon Master's Guide 263) (1,000+ gp; 0 lbs.), in part, says, "Once per day on command, a pearl of power enables the possessor to recall any one spell that she had prepared and then cast. The spell is then prepared again, just as if it had not been cast."
When the caster activates the pearl of power, the spell is reprepared no matter what the caster's done to the spell.
For example, a caster prepares the 5th-level Sor/Wiz spell summon monster V [conj] (Player's Handbook 286–7) that was modified by the metamagic feat Imbued Summoning (Player's Handbook II 92) (that normally adjusts the slot required for the spell by +1) that, in turn, was affected by the general feat Metamagic School Focus (conjuration) (Complete Mage 45) (that then adjusts a metamgic-modified spell's slot by −1). When the caster activates her pearl of power (5th-level spell), she'll reprepare that 5th-level spell, just as she had when she first prepared it, complete with the Imbued Summoning metamagic modification.
However, repreparing that spell doesn't impact the spells that've been expended due to having been imbued upon a creature via the feat Imbued Summoning! The benefit of the feat Imbued Summoning, in part, says
When you cast a spell from the summoning subschool, you can choose to grant the summoned creature or creatures the benefit of any spell of 3rd level or lower you can cast that has a range of touch. You cast the spell you wish to grant the creature (using a prepared spell or a spell slot) at the same time you cast your summoning spell. The creature or creatures gains the benefit of the spell when it appears.
So the spell that's piggybacking onto the summoning subschool because of the feat Imbued Summoning is a separate spell that's cast independently, therefore unaffected by the pearl. Thus, while the caster gets back the summon monster V spell using the pearl, the caster doesn't also get back her invisibility spell that she used the first time she cast that summon monster V spell.