adb - .apk file getting removed from /system/app directory on android 4.1.2 -

i trying install app on android 4.1.2 using adb shell. app in development works on higher android version placed under /system/priv-app/ directory. doing

su mount -o remount,rw /system cat /sdcard/myapp.apk > /system/app/myapp.apk chmod 644 /system/app/myapp.apk reboot 

before reboot verified file placed under /system/app correct permissions. when phone reboots app seems getting cleared /system/app directory , don't see there anymore. clues?

i got problem, happening because htc 1 android version 4.1.2 , api used in app supported on version 4.4.3 or above. when android rebooted not able launch app , hence removes it.