Hi leela
Never give up hope
I have had a request to a band via venue, and I haven't seen anything back from them (it's been over 1 1/2 months.)
It's probably definite that they have passed on your request to Coldplay (most likely their management.)
The thing is, some bands prefer to collect all mail that comes to them and then answer it all at once at the end of their tour, and others prefer to answer them while they're at the venue. It really depends on how much time they have to sign, how many requests recieved, how busy their schedule is etc.
Coldplay still have a while in their tour to go (they'll be coming down to Australia in a few months

.) Since you've included an IRC, it's possible that they could sign at a later date and return your photo to you (whether it be at another leg of their tour, or when they get back home at the end of the tour.)
It's not unusual for some people to have waited months after writing via venue for their request to come back, others in a matter of days. I guess it comes down to luck and patience.
You have nothing to worry about leela. Good luck, and I wish you all the best in getting your response back from Coldplay soon. I can't wait to write to them when they tour here soon
nowandagain [rockon]