Don't think it's embarrasing, not at all. I've been in that situation many times before. As I mentioned above, check
/var/log/messages. Normally the Linux kernel will start logging with something like this:
Code:
Jul 29 17:44:17 darkstar syslogd 1.5.0: restart.
Jul 29 17:44:17 darkstar kernel: klogd 1.5.0, log source = /proc/kmsg started.
By examining the log you'll know if the computer was turned on while you were away. But there are better security measures, most BIOSes can be set up with passwords, and boot managers can also have passwords. Hard disk partitions can be encrypted, which is very useful with laptop computers.
If you use one or more security measures, casual unauthorized users will have a hard time accessing your system and data.