I've had trouble with gmail in the last few days myself. Sent 2 important e-mails which apparently never arrived. Luckily the recipients got back to me to ask why I'd not replied to their e-mails and so I realized there was an issue.
No fix. Just went onto my iphone and it did the same thing - refreshed my inbox and deleted a weeks worth of email. We are moving to the US in the summer and that includes all the admission letters from the schools!!
Has anyone else had this problem? Everything was normal until about 10 mins ago and I returned an email and now my inbox is only showing email to March 30 - last 5 days not there!