Disappearing emails

I have spent hours searching for an email I KNOW I sent.... In frustration I went to 'setting' in gmail and 'ungrouped' conversations and PRESTO the email was there.... When I regroup the conversations it disappears again totally... not in any threads, not in 'sent' mail... (not even coming up on a full email search)...... I have NO IDEA why this is happening.... All I know is that it is happening, it shouldn't happen and I am turning from being a total APPLE fan... to wondering how I can switch back to a wiondows based system. Totally fed up with Apple recently ... I wish I didn't have Iphone, Ipod touch, Ipad AND MacBook Pro...... changing is going to take a while but I will change unless Apple does something to stop these annoying quirks....