Ive read the Offqual repprts and sanctions lists. Mobile phone and other electronic devices were down to 790 offences in 2015.
The penalties fall into three types. Bringing a phone into the exam area, which will get you a warning, having a mobile phone on you, but no sign of usage will get mark deductions and usage which gets you varying degrees of disqualifcation.
Still find it a bit baffling why you dont check as you will get asked plenty of times about what you can and cant have with you. I would have a ziplock bag with everything in, that I could pick up in the morning and take with me, knowing it contained everything. Pupils should be well enough drilled at doing exams by the time they come to GCSEs, so not much excuse really. That said and I said it already thing happen and I hink the OP as soon as she realised reacted in the best way possible.