I'm not too sure what were the reasons put forth for their assessment that the price will go down after it has been released. Was the reason of the likelihood of increasing interest rates being cited?
I might be wrong, but you also seem to have the idea that an asset which has a fluctuating price is automatically classified as a stock?
I think you need to first distinguish that fundamentally, buying the bond of a company versus buying the stock is that the former is equivalent to lending money to the firm whereas the latter is buying a stake in the firm, aka you become one of the owners.
Anyway back to your point on the $2000. For the bond you purchased, the firm is legally obliged to pay you the coupon payments (interest for borrowing) and then pay you back the $2000once the bond matures. On the contrary if you purchased $2000 worth of stock, there is nothing in place to say, after so and so years, your $2000 will still be there should you decide to sell off the stock.
If you want to go into the textbook differences, there is a whole list of differences, which you can easily google.
One key factor that affects your bond price is interest rates. Here is a rather straight to the point explanation of their relationship:
Relationship Between Bonds & Interest Rates - Wells Fargo Advantage Funds
Other factors can also include things like downgrade of the issuer's rating. I.e The firm is deemed to be riskier and has a higher chance of default.
In this scenario, you can think of it as if you were to lend say $1000 to two fellas, where one fella is a compulsive gambler and the other who doesn't know what ban luck is. Who would you likely lend to? And if you did lend to the gambler, shouldn't you ask for a higher interest payment to compensate for his risk of default?
In times of bear runs, investors also typically shift money to bonds, so market conditions can also affect bond prices.
Note: I am not very well read about bonds, please feel free to add on or correct!