Yes, carbon fibre loses all its structural integrity if exposed to rain. It is very serious and it is very dangerous.
Worryingly, it continues to appear unaffected for several weeks after the critical change occurs at a molecular level.
Although the frame will look to be in perfect condition, it is not. It will turn to marmalade quite suddenly, usually during a high-speed descent.
If you send the frame to me, I can dispose of it in an environmentally friendly fashion. Make sure you do not remove any of the ancilliaies, the crank, chain, wheels or saddle. Loosening any clamp, QR or allen bolt could result in a sudden and catastrophic failure of the space-time continuum.
This does not happen to aeroplanes, rowing eights or F1 cars as they are made of a special, magic carbon fibre that cannot be used to make bicycles.
PS. If your frame is not 51 or 52cm, you're OK. This chemical change only happens to frames of 51 or 52 cm. Top-end Campag componentry preferred.
Thank you.