There's the problem, you just explained the mistake you did. You took off the lid and exposed the plant to dry air without letting it acclimate, so it's in shock. Fortunetly you had it's soil moist that it survived.

What happened is the hair on the current leaves were damaged and its tentacles dried out, so they are not going to produce dew, you will have to wait for the new leaves to sprout to replace the damaged leaves. But sundews do recover from shock quickly and acclimate just as fast. All you have to do is simply wait for the new leaves to develop.

Thanks for the response, hunterkiller.

What should I do now to prevent any more damage? I've been keeping the lid on, should I take the lid off for a couple hours a day or just take it off completely now?

I guess you both don't realize it needs to be acclimated to full sun also. It may not survive if it was in full sun the entire time you were gone. You need to acclimate it to less humidity first then to full sun. Prop the lid up with something and raise it a little every day. In about a week or so when it gets plenty of air, you can start acclimating it to full sun. Start with an hour or 2 in the morning and increase the amount of sun by an hour or 2 each day until it gets sun all day. Good luck and hope it survives after it's experience with sudden full sun.

The reason I didn't said the plant needs to be acclimated like you said is... Well... to late for that.

Despite the leaves tentacles were damaged by the dry air. The leaves look sturdy enough. The flower stalk is growing & doesn't seem wilted, plus the new leaves looks like they're developing healthy. So keeping it in the south-east facing window inside his house is a good move.

It's just a matter of letting the sundew recover.

Reading my post, I should learn to proof read it. I was laughing to myself: "hair on the current leaves were damaged and its tentacles dried out" I hope you understood I meant to say the air dried the tentacles of the current leaves...