Has my truck been tampered with?

So I have a 98 tacoma and it seems lower.  I may seem paranoid and whack
but my X is a sociopath and parted out my last truck.  To the point that it would
not start, I donated it.  With that said i'm extremely suspicious of somethng
happening to this truck.  Im aware of the creeps jacking catalytic converters and
flipping trucks so im kinda losing my mind over it.  I just got it back from
mechanics for a tune up and o2 sensor sitch. and ws driving when something
slammed up under either the hood or the floor board passenger.  It sounded like
I imagine a bungee cord slapping.  No belts are broke and nothing was in
street.  And my truck seems lower.  He took leaf springs from last truck but I
was away so he removed the bed.  He couldnt do that now so im curious is
there something underneath truck that a dirt bag could get to that would affect
the lift and height of truck. Im only 5' tall so Im pretty aware of the the height
because I couldnt touch the middle of the hood with out standing on step stool
whereas, now i can. I apologize if this all sounds crazy.  Welcome to my world.  
BTW; he and his concubine are mechanics so they are hip to hop on cars and
trucks hence, my last truck and have all necessary tools. Any feed back would
be appreciated.