I was playing Minecraft when I planted and bonemealed some seeds, then broke them, only to see that my seed drop disappeared and I was left with only a piece of wheat. I searched my whole entire inventory, but there were no seeds, and I had no hoppers or hopper minecarts nearby that could have possible collected the seeds. I am using the regular texture pack, with Vanilla Minecraft 1.17 on Bedrock Edition(PE) in a singleplayer world.
When you harvest wheat, there is always a chance for it to not drop any seeds, while it will always drop 1 wheat. From the wiki article on wheat:
When a fully-grown wheat crop is harvested, it drops 1 wheat and 0 to 3 wheat seeds. A wheat crop has a total of eight stages (0-7) from the time it is planted until it can be harvested. If a crop is harvested before it is fully grown, it drops one seed. Wheat needs light to grow; a seed is destroyed if planted without light. Harvesting with a Fortune-enchanted tool increases the number of seeds dropped but does not increase the yield of wheat.
I do not know exact numbers for the different possible results, but it sounds like you're just getting some bad RNG, hope it turns around for you soon!