Sorry to hear that. Shrimp are pretty oblivious to what's outside the range of their antennae. In a closed space like an aquarium it's only a matter of time until a predator gets the right opportunity to have a snack.
I have amanos with angels a long time ago (like four years ago) in a 30H. I didn't see the eight shrimp for a year or more, then one day my 30-year-old tank sprung a leak and I drained it and cleared it out...low and behold under the rocks in gravel cavities were my eight amano shrimp.
They had just become adept at hiding and coming out only at night so I never saw them.
I bought 15 cherry shrimp and after the night i put them in the tank them i diddnt see them once. About five months later I saw one on my moss, ever since then I see more and more everyday. So who know maybe there in there somewhere.
My shrimps were also getting eaten by my fish untill my plant mass got thick and dense. Now the shrimp are surviving and multiplying but not as much as a tank with no fish and most shrimps i have dont venture out in the open.
How long were they in the tank? Like DMH said, they're good at hiding. I didn't see my initial bunch of shrimp for two weeks because they were hiding. But once they adjusted they were all over the tank.
I highly suggest throwing in a nice size mat of Java Moss. You'll be able to watch the shrimp feed on the food that gets trapped in it.
Angels pretty much eat anything that will fit into their mouths. Since Cherry's are so tiny they make a nice little treat for them. Even so you still may have some hiding out in your plants, they may emerged later as full grown adults.
About 3 months after putting several amanos in my 29 gallon heavily planted tank with a full-grown angel, I finally saw one of them. It disappeared into the plants again after a few minutes and I haven't seen it since.
I've had lemon tetra breed many times in the tank and over a dozen fry have survived because of the dense growth (one or two fry per spawn). They don't come out of the plants until they're over 1/2" long, and I've never managed to see them when they're smaller.
Of course a lot depends on how much of a hunter your angel is. Mine is pretty darn lazy and waits for the food to fall in front of her mouth sometimes before she'll go for it.
Some angels are a lot more aggressive than others...yours probably enjoys fancy/expensive food.
I've seen many different kinds of fish pick apart freshwater shrimp (even guppies), but I would also second the other comments about how well they hide. Unless you have a shrimp only tank, typically there are 5-10 shrimp in the tank for every one you can see. I've found it easiest to see them by checking when my lights first turn on (or before they turn on, with a flashlight...), or by adding some zuchinni or other vegetables to a spot consistently.