i got 1 striata as my first loach. i had no idea they needed to be kept in groups, i got her from a reputable shop and was assured 1 was fine (but they did only have 1 in). she was very shy and i hardly ever saw her. i managed to get a second one after a while, and they were still quite shy. i now have 8, and would still like more.
fatty, my original loach, is the boss of the tank, and keeps my big yoyos under control now

she is very confident and swimming around a lot. one of my small ones has an eye problem on one side and i think the eye is blind. i only ever see it when its hungry and it swims in shady areas waiting for food. the others are not as bold as the yoyos or as nosy as the rostrata, but will be active at feeding time, and during the evenings. daytimes most of my loaches cant be seen at all. sometimes when we have visitors who want to see the fish, i put some food in, and only the bravest ones will come out - even though i have a yoyo who will dance at the front of the tank begging for food when everything is normal.
it is funny to watch several striata go over to get their sinking pellets, and pick whole ones up and carry them over to a quieter part of the tank. they have great behaviour when you do see them out, so please dont worry aboutthem being shy for now. hopefully they will get used to your house and your family's habits, and become braver soon. they MUST have lots of places to hide in - completely hide - or they will stay shy i think.
some fish seem to be daytime fish, others seem to be evening fish, you may find that yours are just more comfortable being out and about at a different time of day than you had hoped.
please make sure that if you want to get more laoches, increase the number of striata, it will help them get braver. i have watched mine get more confident as i have added more. if i could start again, i would have one big tank with just striata (lots of them!) and dither fish. they are very varaible in their markings, so they are always interesting to look at