Could an electrically charged person damage an ESD sensitive component, that is isolated from ground, by touching it?
While it is less likely to create hard-faults with Electrostatic Charge in a component that is not connected to any bulk surface to dissipate or equalise the initial impulse, it is still possible.

Say you are negatively charged compared to the chip, that means you have "excess electrons", so when you tough a pin of the device, that pin will be connected to your excess and will "want" to become the same charge. This induces a current. It may be shorter in duration and could be smaller than when the chip is "grounded", but it can be enough to kill it, depending on the chip's innards.

Even the over-charge on one pin compared to another can destabilise some constructs in Chips, especially MOS devices, sometimes even permanently.



Note about "Anti-Static" bags, There's a couple types:


Pink Anti-Static: Not safe at all for ESD sensitive chips
Black Dissipative: Very safe for ESD sensitive devices, but less so than the metal-foil ones.
Metal Foil Conductive: Extremely safe.  


The Pink bags are only anti-static: It does not create charge when rubbed by another surface. So they are nice in a shipment with several bags, to prevent static to build up, but a human-body zap can very easily go straight through the plastic to any chip.

The black dissipative actually conducts a bit of electricity, usually a few hundred kOhm to a MOhm per square of resistance, and they will dissipate any charge built up across it and human-body discharges are extremely unlikely to penetrate the bag to the chip, but high level discharges may still affect the chip.

Metal foil conductive: The name says it all, has a very low resistance per square. Some bags have the foil (or a micro-laser-perforated foil to allow some see-through) on the inside, some have an extra layer of dissipative material over it, to protect the metal film. It will be extremely hard to have any kind of zap go through the bag, as the foil will conduct it from one side to the other. Even high intensity discharges will have trouble getting through, with the exception of discharges that will vaporize the foil, since that will make the bag (and chip) explode. And of course a few below that level, but I wanted to conjure the image of an exploding ESD bag.