First of all, most (all?) digital data is "clocked". This means that, while the data line(s) may be high or low at any time, the receiver only looks at the state of the line at a certain time.
In this case, there is another wire with a clock signal on it. This clock signal tells the receiver exactly when to look at the state of the line. In this case, it's on the rising edge of the clock, the exact time at which the voltage goes from low to high. You may have many data lines and one clock line (usually parallel), or one data line and one clock line (serial). There are exceptions to this terminology when you have bidirectional data flows.
You can see here then, that as long as the clock signal is being received, bits will never be "lost". There may be noise on the data line which causes a bit to be read as a 0 instead of a 1, or vice versa, but either way it will still be one bit (if the clock line is noisy it can cause other issues).
This is known as synchronous transmission, but there also exists asynchronous transmission. This is where there is no clock line, and instead both the receiver and transmitter agree to check the line at the same time interval. There is usually some stuff done on the data line to help with initial synchronization. As you can imagine, this requires that the receiver and transmitter both agree on when exactly to sample, and are both quite accurate time-wise.