2003 Front Brake Grinding on left side after driving awhlie.

Hi, I looked in the other posts but didn't see anything like what I am experiencing. My 2003 Grand Caravan (155,000 miles) had the front rotors and ceramic pads replaced by me. I've done this before. Anyway, this replacement was done last summer, about 8-9 months ago. Everything has been fine, until a couple of months ago. Only about five thousand miles have been driven since. Now, the braking is fine until I drive awhile, say 5-10 miles or so, general driving, no highway, just stops every so often in a suburban area. Then, at a certain point, the left front brake seems to begin grinding when I depress the pedal. I pulled the wheel off yesterday, and found the inner brake pad clip the it fits into missing on the top. I went down and got another one and installed it. Looked everything else over, and reassembled. Things seemed fine after road testing on about a 15 mile drive. Now, this morning, the problem has returned! Problem will go away after it is parked for a couple of hours, then after driving for a few miles, will return. By the way, the rotors and pads have very little wear from last year's renewal, so I am stumped as to why this is happening. Any ideas from anyone would be greatly appreciated. Thanks for reading, Bill